In a library the ratio of story books and other books is 7 : 2 and there are 1512 story books. Due to collection of some more story books the ratio becomes 15 : 4. The number of story books collected is = ?
A. 108
B. 205
C. 100
D. 97
Answer: Option A
Solution(By Examveda Team)
According to the question,$$\eqalign{ & \frac{{{\text{Story books}}}}{{{\text{Other books}}}} = \frac{7}{2} \cr & {\text{Story books = 1512}} \cr & {\text{7 units}} \to 1{\text{512}} \cr & {\text{1 unit}} \to \frac{{1512}}{7} = 216 \cr & {\text{2 units}} \to 216 \times 2 = 432 \cr & {\text{Other books }} = 432 \cr & {\text{New ratio of}} \cr & \frac{{{\text{Story books}}}}{{{\text{Other books}}}} = \frac{{15}}{4} \cr} $$
As we know that only story books are added
$$\eqalign{ & {\text{4 units}} \to 43{\text{2}} \cr & {\text{1 unit}} \to \frac{{432}}{4} = 108 \cr & {\text{15 units}} \to 108 \times 15 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 1620 \cr} $$
New collection of story books = 1620
∴ Number of story books are added = 1620 - 1512 = 108
Related Questions on Ratio
If a : b : c = 3 : 4 : 7, then the ratio (a + b + c) : c is equal to
A. 2 : 1
B. 14 : 3
C. 7 : 2
D. 1 : 2
If $$\frac{2}{3}$$ of A=75% of B = 0.6 of C, then A : B : C is
A. 2 : 3 : 3
B. 3 : 4 : 5
C. 4 : 5 : 6
D. 9 : 8 : 10
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