Reversability_Maths

For maths today, my group, taha, were focusing on one strategy. This strategy being, Reversability. We had to answer the problems below, and show our working out, creating a diagram like the one below. Here are the problems and my final answers. 

Last week we worked on using reversibility to solve problems in addition and subtractions. Below is an example of how you can use reversibility.

Problem 2 Sarah has $466 in her bank account and spends $178 on a new phone, how much money does she have left in her bank account?

Reversibility:

$466 - $178 is the same as saying how much do you need to add to $178 to get $466. $178 plus $22 makes $200, plus $200 more makes $400 plus $66 makes $466. If you add up $22 plus $200 plus $66 you get $288.

Solve these problems using reversibility. Please show your working out like the diagram above.

1. Sarah has $288 in the bank. She then deposits her pay cheque for $127 from her part time job at PetCare. How much does she have now? 161
2. 628 - 342=286
3. 537 - 261=276
4. 742 - 353=389
5. 1521 - 754=767
6. 1762 - 968=794
7. 1656 - 867=789
8. Sally had 10032 buttons. She sold a collection of 1028. How many does she have left? 9004
9. Susan had 1083 centimeters of ribbon. She used 893 centimetres on a project. How many centimetres are left? 190 CHALLENGE - how many metres is that? 1 metre and 90 centimeters: 1.9
10. Tawhiri cycled 3872 metres of a 10729 m race in three days. How many more metres does he have to cycle?

6857m

Here are the reversibility diagrams that I had drew. In the images, it also contains my answers and how I worked it out.