A smartphone!
John, Jack and Tom are brothers. They have 300$. John have 25% of this money and Tom have 90$. John wants to buy a smart phone which price is 125$. If he wants to borrow money from his brothers in equal proportions (according to the amount of money they have) to have enough money to buy it (in addition to his money). How much money would he borrow from Jack? (in Dollars)
The answer is 30.
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1 solution
Let the amounts John, Jack and Tom each has be A J o h n , A J a c k and A T o m respectively. Then,
\(\begin{array} {} A_{John} = $300 \times 30\% & = $75 \\ A_{Tom} = $90 & = $90 \\ A_{Jack} = $300 - $75-$90 & = $135 \end{array} \)
The amount John needs to borrow is B = $ 1 2 5 − $ 7 5 = $ 5 0 .
The amount he needs to borrow from Jack is:
B J a c k = A J a c k + A T o m A J a c k × B = 1 3 5 + 9 0 1 3 5 × $ 5 0 = 2 2 5 1 3 5 × $ 5 0 = 5 3 × $ 5 0 = $ 3 0 .