Question

If a sprinkler waters 1 over 20 of a lawn in 1 over 5 of an hour, how much time will it take to water the entire lawn?

3 over 20 hour
1 over 4 hour
4 hours
5 hours

Answer 1

Option 3

Time taken to water entire lawn is 4 hours

Solution:

Given that sprinkler waters 1 over 20 of a lawn in 1 over 5 of an hour

To find: time taken to water the entire lawn

So 1 over 20 of lawn is watered in 1 over 5 of hour

We know that 1 hour = 60 minutes. So 1 over 5 of hour means,

$1 \text { over } 5 \text { of hour }=\frac{1}{5} \times 60=12 \text { minutes }$

Thus 1 over 20 of lawn is watered in 12 minutes

Let "a" be the time taken to water the entire lawn

If 1 over 20 of lawn is watered in 12 minutes, then entire lawn is represented by $\frac{20}{20} = 1$

$\frac{1}{20} \rightarrow 12 minutes\\\\1 (entire lawn) \rightarrow a$

On cross multiplication we get,

$\frac{1}{20} \times a = 12 \times 1\\\\a = 12 \times 20 = 240 minutes\\\\a = \frac{240}{60} = 4 hours$

Thus the time taken to water entire lawn is 4 hours

Answer 2

Answer:

Option 3, 4 hours

Step-by-step explanation:

When you work with this problem you can switch the fractions as so,

1/20 x 5/1

= 5 / 20

Now, we have a simplified fraction.

In order to find the answer (because this isn't up there on the list) we divide.

$Numerator / Denominator$

     $5$                     $20$

=    $4$

Therefor, the answer is 4 hours