John and Walter have their incomes in the ratio 7 : 5. The expenses of John, Walter and Nancy are in the ratio 9 : 7 : 4. If Nancy spends $2800 and Walter saves $1100, how much is John’s saving is?
A) $2000
B) $2100
C) $2200
D) $2300
Solution: There is some common element hidden in these type questions pertaining to Ratio and Proportion. If you can find that out, the rest of the solution is a cakewalk.
Let the expenses of John, Walter and Nancy be 9y, 7y and 4y respectively.
Thus, 4y = 2800
=> y = 700
Now, let the incomes of John and Walter be 7x and 5x respectively.
Equation(1)…………Income – Expense = Saving
Plugging in values for Walter,
5x – 7y = 1100
=> 5x – 7*700 = 1100
=> 5x = 1100 + 4900
=> 5x = 6000
=> x = 1200
Plugging in values for John, we get,
7x – 9y = Saving
7*120 – 9*700
=> 8400 – 6300
=> $2100
Thus, John’s saving is $2100
Correct Answer: B
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