How many seconds are there in 7 3/8 minutes?

Question

$7 \text{ minutes} \cdot 60 \frac{\text{seconds}}{\text{minute}} = 420 \text{ seconds}$

What about the other $\frac{3}{8}$ minute?

Answer 1

You do the exact same thing:

$\frac{3}{8} \text{ minutes} \cdot \frac{60\text{ seconds}}{\text{minute}} = 22.5\text{ seconds}$

Which makes your answer: $420+22.5\text{ seconds} = 442.5\text{ seconds}$

Answer 2

You do just as you did with $7$ minutes; multiply by $60$:$$\require{cancel}\frac{3}{8} \cancel{\text{ minute }}\times \frac{60\text{ sec}}{\cancel{\text{ minute }}}= \dfrac{3\times 60}{8} \text{ seconds}$$

Now just add that to the seconds you found in $7$ minutes.