# 346. Area & Volume conversion

This is a quick post on how I teach metric unit conversion for area and volume. All you need is a big whiteboard and coloured board pens.

Start by stressing that all diagrams are not to scale/accurate.

Two colours

1. Draw a square on the board
2. Pen colour 1: Label it as 1cm
3. What is the area? Show the calculation
4. What is 1cm in mm?
5. Pen colour 2: Label it as 10mm
6. What is the area in mm? Show the calculation
7. What is the scale factor between the sides? the area? why?

Three colours

1. Draw a square on the board
2. Pen colour 3: Label it as 1m
3. What is the area? Show the calculation
4. What is 1m in cm?
5. Pen colour 2: Label it as 100cm
6. What is the area in cm? Show the calculation
7. What is the scale factor between the sides? the area? why?
8. Repeat in pen colour 1 for mm

Four colours

Well not actually four colours – pens 2,3 & 4 only. Repeat the process for kilometres to metres and centimetres.

Volume – same process, just three dimensions

Why all the colours?

By coding each unit of measurement with a colour students can see the progression of the calculations and the links between area/volume and scale factor. After all, an okay mathematician can reproduce memorised facts, but a great mathematician doesn’t need to memorise – they understand where the calculations came from.

# 345. Practical percentage skills

It’s perfectly obvious that fluency in the use of multiplication tables directly impacts students ability to divide. This grows into confidence with algebra and reverse operations. Students are able to see the links between the concepts. Our understanding of the importance of such skills is part of the success of programmes such as TTRockstars and Numeracy Ninjas.

Why is it then that so many textbooks, websites and resource banks keep the manipulation of percentages as separate skills sets? Percentage increase / Percentage change / Reverse percentages. We know that when concepts overlap, fluency increases when these links are pursued. So that’s what I set out to do.

I have a bright Year 8 class and started working on percentages with them. It didn’t take much to have them confident using equivalent decimal multipliers to find percentages of amounts. Using a multiplier for increase/decrease was a walk in the park. Then finding percentage change came up. Over the years I’ve seen a lot of students get very confused with half remembered methods:

“Which do I take away?”

“What number do I divide by?”

“Is this calculation the right way around?”

I tend to teach new value divided by old value and interpret the answer. It got me thinking – why am I teaching them this? They can increase by a percentage using a multiplier, why can’t they rearrange their working to find the actual percentage? Same goes for reversing a percentage.

After a good discussion, I used this worksheet to recap and develop their skills:

Warning: “Original Amount” section, question (d) is a tricky one.

As with all new approaches, it’s always good to see if it worked. I set the following task from Don Steward’s website:

MEDIAN percent problems

I have GCSE students who wouldn’t know where to start on those questions, yet my Year 8 with their ‘have a go’ attitude were absolutely awesome. I’m definitely using this method again!

# 343. Butterflies, dreams and stories: How to say goodbye

It’s finally here. My Y11 form group are going on study leave next week. I’ve been their tutor since the summer of Y8. They really are a lovely bunch of students. I’ve been planning their goodbye for some time.

Dreams

Since Year 9 I’ve periodically given out “100 things I want to do with my life” sheets. I found the image on Pinterest. They’ve added their aspirations over the years. Some are more detailed than others, depending how seriously they took it.

Butterflies

Inspired by the origami of Clarissa Grandi and her amazing website, at the start of Year 10 each student made a butterfly. Each student wrote a hope or dream or positive message on a coloured luggage tag. They attached the luggage tag to their butterfly and I put them up on the wall. They’ve been there ever since.

Stories

I wrote a silly story with every students’ name included. Some are obvious, some are sneaky.

Finally

I put each ‘bucket list’ back to back with the story, then laminated them (if students want to add to their lists they can just use a permanent markers). Each laminated sheet was rolled up and secured with a cheap hair elastic. I then slipped the luggage tag under the band. They look like graduation scrolls.

All these things could be done in a much shorter period of time. I think they will be a personalised memory of their time at school.

# 342. Revision jotters

With the exams looming large, I thought I’d share how my class have been revising. To give you some context roughly a third of the class are doing Foundation GCSE, aiming for at least a Grade 4. The rest are doing Higher and aiming for a Grade 5 or better. We have three, one hour, lessons a week. I’m rotating between doing an exam paper, a whole class revision activity (eg a revision clock) and tiered revision.

I know if I tell the students to revise independently the results are going to be mixed. Some will be brilliant, some will be more laid back. To resolve this I pick a topic (or two) from each tier that I know they need to improve on from or that they have requested. It’s helpful if there is a theme to the work. I’ve recently done things like y=mx+c (F) with plotting inequalities (H).

Now the genius part: PixiMaths revision jotters

How to run the session

Photocopy a big stack of revision jotters. If you are doing black and white copying, use the b&w version. We requested the b&w version and, because PixiMaths is awesome, it is now on the website.

Clearly put on the board which topic each tier is revising

Eg Foundation: exact trig values, Higher: trig graphs

Give students 5-10 minutes to fill their revision jotters with everything they know. Have textbooks or maths dictionaries available to fill in the gaps. You may find that Higher students want to do the Foundation topic too – no problem, just make sure they have two jotters. Due to the complexity of the Higher topic, they will need more time to make initial notes.

My students are allowed headphones in revision sessions. At this point it’s headphones in for Higher and out for Foundation.

Do a skills recap on the board (exact trig values), with maybe an exam question too. Students can ask questions on the topic and add to their jotter. Then have a worksheet for students to do eg Corbett Maths or KeshMaths GCSE exam questions booklets. They can refer to their revision jotter or scan the Corbett Maths QR code for extra help.

Swap over. Headphones in for Foundation and out for Higher.

Repeat the process for Higher, with drawing trigonometric graphs. Issue an appropriate worksheet.

Once you’re done, make a judgement call. Are there students who could push it further? Maybe transform a trig graph or problem solve? Go for it. Foundation are busy, Higher are busy, spend some time stretching your most able. Every mark counts.

A huge thank you to PixiMaths for the revision jotters (and everything else).

Examples of students’ work

Shared with permission of students. You can see that they have personalised them to meet their needs and some are a work in progress. Also, the b&w jotter photocopies so nicely.

# 341. Dragon Bridge

Here is a little starter picture for you:

This is the ‘Pont y Ddraig’ at the marina in Rhyl, in North Wales. What mathematical questions could be inspired by this?

‘Pont y Ddraig’ means Dragon Bridge. Find out more about the bridge here

# 340. SUVAT dilemma

If you’ve been a regular reader of this blog you may remember a post in 2014 advocating the use Duck Tape to help with practical investigations. The post was: http://mathssandpit.co.uk/blog/?p=1585

I’ve recently reused the mechanics activity with a new class of Year 12 students. They had only just started mechanics and were familiar with models and suvat equations. We timed four different objects being dropped, under gravity, down a stairwell. The items had a variety of masses: a paper helicopter, a light plastic ball, a small sponge and a dense juggling ball. We meticulously timed each drop and double checked the height.

I asked the students to work out the velocity of each object on impact with the ground. It was akin to lighting the blue touch paper and standing back …

They are a competitive bunch and raced ahead to use the correct suvat equations to calculate the velocity. Then the fireworks started!

Part of the class insisted that the juggling ball must have the highest velocity. Part of the class insisted the velocities were the same for all of the objects. The rest were catching up and wondering what all the discussion was about. I innocently gathered their ideas on the board and asked them what was going on. Those who had used initial velocity, time & distance to find the final velocity had differing answers for each object. Those who had used initial velocity, distance and acceleration had a consistent answer.

Suddenly a hand shot up and said “Because we model objects as particles, their mass doesn’t matter so we can’t use the times”. This was followed by assorted groans from the class – especially those who’d used the individual times of the objects.

The variation of the original activity was to emphasise prior learning on setting up mathematical models for solving mechanics problems. Objective achieved!

(Obviously later in the course we’ll look at the impact of mass on mechanical models, but this was early days)