Question

Ratio of lemon to water to be mixed to prepare lemon juice is 3:5. For 12 lemons the number of cups of water to be used is:
A.10
B.15
C.20
D.25

Answer 1

Hint: This question can be solved by concepts of unitary method. For 3 parts lemon, 5 parts water is used. It is to be found, for 12 lemons the number of cups.

Complete Step by Step answer:
A ratio is the quantitative relation between two amounts showing the number of times one value contains or is contained within the other. In mathematics, a ratio indicates how many times one number contains another.
It is given that, ratio of lemon to water to be mixed to prepare lemon juice is 3:5.
Thus, for 3 lemons, 5 cups of water is used.
Using the unitary method, it can be said that, for 1 lemon, $\dfrac{5}{3}$cups of water is used.
For 12 lemons, $\dfrac{5}{3} \times 12$ cups of water are used.
Thus the number of cups used is, $5 \times 4$ cups of water.
$\therefore $ For 12 lemons, number of cups of water $ = 20$ cups of water.

Hence, the correct answer is Option C.

Note:
The comparison of two numbers or quantities by division is known as the ratio. For a ratio, the two quantities must be in the same unit. If they are not, they should be expressed in the same unit before the ratio is taken. A ratio may be treated as a fraction.
Four quantities are said to be in proportion, if the ratio of the first and the second quantities is equal to the ratio of the third and the fourth quantities. The method in which first we find the value of one unit and then the value of the required number of units is known as the unitary method.