(a)
Find the sum of 3985 and 1273.
Notice that the word sum is used but this means add
Quickly estimate the answer
4000 + 1000 = 5000
Write the numbers in two rows and columns aligned
Start with the ones (units) column, writing the answer below the line but in the same column
Move on to the tens (next on the left) column
The sum is 15 so the 5 (ones) is written below the line and the 1 (tens) 'carries over' to the next (hundreds) column
Next is the hundreds column which again results in a two-digit answer
Finally add the digits in the thousands column
Check the final answer is similar to your estimate; 5000 and 5258 are reasonably close
3985 + 1273 = 5258
(b)
Find the difference between 506 and 28.
Notice that the word difference is used; this means subtract
Quickly estimate the answer
500 - 30 = 470
Write the numbers in two rows, column aligned, ensuring the top number is the number being subtracted from
In the ones (units) column, 6 is smaller than 8, so borrow from the next column (tens)
The tens column is 0, so borrow from the column to the left of that (hundreds)
This turns the 0 (in the tens column) into a 10 which we can then borrow from (for the ones column)
16 - 8 can be now be calculated in the ones column
Move onto the tens column which is 9 - 2 = 7
There is nothing to subtract in the last (hundreds) column (4 - 0 = 4)
Check the final answer is similar to the estimate; 470 and 478 are reasonably close
506 - 28 = 478
(c)
Johnny has £32.50 and spends £1.74. Calculate how much money Johnny has left.
This is a subtraction question as Johnny has spent money
Quick estimate
33 - 2 = 31
Align the digits by place value, ensuring £32.50 is the top number and using the decimal points as a starting point
Using place value holding zeros is optional
The column furthest right is the hundredths column
0 is smaller than 4 so borrow from the next (tenths) column
Next is the tenths column, but again 4 is smaller than 7 so borrow 10 from the ones column
14 - 7 = 7 in the tenths column and continue working 'right to left'
Check the final answer is similar to the estimate; £31 and £30.76 are reasonably close
Johnny has £30.76 left