Question

At a certain fast food restaurant, Brian can buy 3 burgers, 7 shakes, and one order of fries for Rs. 120 exactly. At the same place it would cost Rs. 164.5 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 order of fries?
1. Rs. 31
2. Rs. 41
3. Rs. 21
4. Cannot be determined

Answer 1

Correct Answer - Option 1 : Rs. 31

Explanation:

Let the cost of 1 burger, 1 shake and 1 fries be x, y and z.

Then,

\(\frac{{\begin{array}{*{20}{c}} {3x + 7y + z = 120\;\;\;\;\;\;\;\;\; \ldots \left( i \right)}\\ {4x + 10y + z = 164.5\;\;\;\;\; \ldots \left( {ii} \right)} \end{array}}}{{x + 3y = 44.5\;\;\;\;\;\;\; \ldots \left( {iii} \right)\left( {ii - i} \right)}}\)

Multiplying (iii) by 4 and subtracting (ii) from it, we find

2y – z = 13.5    ---(iv)

Subtracting (iv) from (iii),

∴ We get x + y + z = 31.