A stationery shop ordered 8 dozen red pens and some additional dozen blue pens. The price of the red pens per dozen was four times that of the blue ones. When the order was delivered, it was found that the number of dozens of the two colors had been interchanged. This increased the bill by 50%. Find the ratio of the number of dozens of red pens to the number of dozens of blue pens in the original order.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 1:2.
Let Blue pens = x dozen
Let Price of blue dozen = 1 and Red dozen = 4
Original bill = 8 × 4 + x × 1 = 32 + x
After interchange = 4x + 8 × 1 = 4x + 8
So, 4x + 8 = 1.5(32 + x)
⇒ 4x + 8 = 48 + 1.5x
⇒ 2.5x = 40
⇒ x = 16
Red : Blue = 8 : 16 = 1 : 2