Written algorithms for subtraction Decomposition Algorithm - Explanation using 74 - 38 Thinking text Algorithm Using place value materials 74 subtract 38. tens ones Reuben makes 7 tens and 4 ones He renames a ten as 10 ones, leaving 6 tens He has now represented 74 as 6 tens and 14 ones Reuben now takes away 8 ones from 14 ones leaving 6 Reuben also takes away 3 tens from 6 tens, leaving 3 tens. Subtract the ones first. There are four ones and eight ones have to be taken away. Rename one of the 7 tens as 10 ones, leaving 6 tens. Tens ones Add the 10 ones to the 4 ones giving 14 ones. 74 is now 6 tens and 14 ones. Tens ones 14 ones take away 8 ones is 6 ones. Tens ones Now subtract the tens. 6 tens take away 3 tens is 3 tens. Tens ones 74 take away 38 is 36.   Back to Teaching algorithms for subtraction