Average cost of 5 apples and 4 mangoes is Rs. 36. The average cost of 7 apples and 8 mangoes is Rs. 48. Find the total cost of 24 apples and 24 mangoes.
Solution:Option(B) is correct
Average cost of 5 apples and 4 mangoes = Rs. 36
Total cost = $36 \times 9 = 324$
Average cost of 7 apples and 8 mangoes = 48
Total cost = $48 \times 15 = 720$
Total cost of 12 apples and 12 mangoes = $324 + 720 = 1044$
Therefore, cost of 24 apples and 24 mangoes = $1044 \times 2$ = 2088
Edit: For counter intutive cost outcome of this question, check discussion.
Error(s) Found !!!
PRATYUSH ANAND (Apr 14'14 at 12:33)
I don't know why answer doesn't come if we use equation in this question.
Let cost of each Apple be $A$
and Mango be $B$
then equation form:-
$5A+4B=36 \times 9$ ---(i)
$7A+8B=48 \times 15$ ----(ii)
$A=-24$ & $B=111$
Is it because here in question we should consider Apple and Mango as same entity,then only answer will come ????
Nothing is wrong, you actually got right answer. The apple cost is actually -24 in this question for these conditions to be possible.
Also 24 apples and 24 mangoes = 24*(-24) + 24*111 = 2088 which is correct :)
while solving cost problems with polynomials of more than first degree you should only consider the positive value from the roots you get while solving the polynomial
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