Question

Dany bought a total of 20 game cards some of which cost $0.25 each and some of which cost $0.15 each. If Dany spent $4.2 to buy these cards, how many cards of each type did he buy?

Answer 1

He bought 12 $0.25 costing cards and 8 $0.15 costing cards.

Explanation:

Let the number of $0.25 costing cards he bought be s,
Let the number of $0.15 costing cards he bought be t,
According to the question,
He bought a total of 20 game cards,
Thus,
s + t = 20
or, s = 20 - t ------(i)
Now,
Since, he bought s and t no of cards each and it amounted to $4.2, we know,
$0.25s + $0.15t = $4.2
or, $0.25(20 - t) + $0.15t = $4.2 [From (i)]
or, $5 - $0.25t + $0.15t = $4.2
or, $5 - $4.2 = $0.1t
or, $0.8/$0.1 = t
t = 8
From (i),
s = 20 - t = 20 - 8 = 12
Therefore, he bought 12 $0.25 costing cards and 8 $0.15 costing cards.