# Eight out of ten fish are trout. How many trout are there out of 40 fish?

Dec 9, 2016

Out of these 40 fish 32 are trout.

#### Explanation:

The ratio relationship for this is $8 : 10 \to t : 40$ where $t$ is the number of trout. Turning this into an equation and solving for $t$ gives:

$\frac{8}{10} = \frac{t}{40}$

$40 \cdot \frac{8}{10} = 40 \cdot \frac{t}{40}$

$\frac{320}{10} = \cancel{40} \cdot \frac{t}{\cancel{40}}$

$32 = t$

Dec 9, 2016

40 is the fourth multiple of 10, which means that $10 \times 4 = 40$.
Then, if 8 out of 10 fish are trout, the number of trout in 40 fish will be the fourth multiple of 8, which is equal to $8 \times 4 = 32$.