Ben has 24 stamps. He buys 46 stamps more from a store. How many stamps does he have now?

The correct answer is: 70

Ben has 24 stamps. He buys 46 stamps more from a store.
Total stamps Ben has = 46 + 24
To find partial sums add the digits in tens place and ones place seperately.
Partial sum of 46 + 24
Step 1 : Add digits in tens and ones place seperately:
40                                    06
+ 20                   and        + 04

_____                             ______
60                                        10
Thus, the sum of 46 + 24 are 60 + 10 = 70.

So, Ben has 70 stamps in all.