Question

Mary spent hour waiting for the school bus and to hour riding the bus to school. How much time did Mary spend in all?

Answer 1

7/10

1) Since May spent:

2/5 hour waiting

3/10 hour riding

2) We'll have to add them up. Since these fractions have different denominators (bottom number) let's calculate the LCM of 5 and 10:

So dividing them by prime numbers, the LCM is the product of 2 and 5 = 10.

So we can write:

$\frac{2}{5}+\frac{3}{10}=\frac{10\colon5\times2+10\colon10\times3}{10}=\frac{4+3}{10}=\frac{7}{10}$

3) Hence, Mary spent 7/10 of an hour in all.