Joel has 27 toys which are in blue in color and 31 toys which are in green in color. How many toys does Joel have in all?

The correct answer is: 58

Number of blue color toys Joel has =27
Number of green color toys Joel has = 31
Total number of toys Joel has = Partial sum of 27 + 31
To find partial sums add the digits in tens place and ones place seperately.
Partial sum of 27 + 31
Step 1 : Add digits in tens and ones place seperately:
20                                    07
+ 30                   and        + 01

_____                             ______
50                                        08
Thus, Total number of toys Joel has = the sum of 27 + 31 are 50 + 08 = 58.