1. Use the mental math strategy of rounding (for example +1/-1, +2/- 2, +10/-10, or +20/-20) to add the following numbers. Write down how you would change the numbers in your head for each question. Ex. 27 + 51 28 + 50 = 78
a. 41 + 16
b. 79 + 14
c. 580 + 355
d. 174 + 620
e. 378 + 210