A sum of ₹ 6.25 is made up of 80 coins which are either 10P or 5P. How many are there of each kind?
(a)45, 35
(b)40, 40
(c)35, 45
(d)25, 55
Answer
Answer (as printed): A
Explanation
Let the number of 10P coins be $x$. Then, number of 5P coins $=(80-x)$. $$\begin{array}{ll} \therefore & 0.1 x+0.05(80-x)=6.25 \\ \Rightarrow & 0.1 x+4-0.05 x=6.25 \Rightarrow 0.05 x=2.25 \\ \Rightarrow & x=\frac{2.25}{0.05}=\frac{225}{5}=45 . \end{array}$$ Hence, number of 10 P coins $=45$. And, number of 5 P coins $=(80-45)=35$.
Explanation as extracted from the printed page; notation may be imperfect.