Using partial sums find the sum of 4 tens & 3 tens 5 ones.

The correct answer is: 75

Here, 4 tens + 3 tens 5 ones = 40 + 35
To find partial sums add the digits in tens place and ones place separately.
Partial sum of 40 + 35
Step 1 : Add digits in tens and ones place separately:
40                                    00
+ 30                   and        + 05

_____                             ______
70                                        05
Thus, the sum of 40 + 35 are 70 + 05 = 75.