At a certain fast food restaurant, Brian can buy 3 burgers, 7 shakes and one order of fries for ₹ 120 exactly. At the same place, it would cost ₹ 164.50 for 4 burgers, 10 shakes and one order of fries. How much would it cost for an ordinary meal of one burger, one shake and one fries?
(a)₹ 21
(b)₹ 31
(c)₹ 41
(d)Cannot be determined
Answer
Answer (as printed): B
Explanation
Let the price of 1 burger, 1 shake and 1 fries be ₹ $x$, ₹ $y$ and $₹ z$ respectively. Then, $$\begin{aligned} & 3 x+7 y+z=120 \\ & 4 x+10 y+z=164.50 \end{aligned}$$ Subtracting (i) from (ii), we get: $x+3 y=44.50$ or $2 x+6 y=89$ Subtracting (iii) from (i), we get: $x+y+z=(120-89)$ $=31$. ∴ Cost of 1 burger, 1 shake and 1 fries = ₹ 31.
Explanation as extracted from the printed page; notation may be imperfect.