b) 6,918

c) 9,891

d) 9,901

2a) 6,330

b) 82,100

c) 27,808

d) 33,841

2) B

3) D

Amir's mistake is that instead of exchanging in the 10's column, he has taken 5 away from 4.

2a) 19,415

b) 75,305

3) Teddy did not exchange in the 10's column and instead thought that 0-5 was 5.

4) 64,112+25,814

b) 64,092 + 25,834

5) Dexter's mistake that is when he has carried the 10's he has put them in the same column, rather than the column to the left.

Eva's mistake is that she has not lined up her calculation and is therefore subtracting the ones of the smaller number from the 10s in the larger number

6) 52,478 - 31,620