A company placed an order for 18 high-end laptops and some quantity of standard desktops. The price of a high-end laptop was 4 times that of a standard desktop. Due to a mistake, the number of laptops and desktops was interchanged in the delivery. This caused the total bill to increase by 100%. What was the ratio of the number of high-end laptops to standard desktops in the original order?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 2:7.
Let the price of one standard desktop = p
Price of one high-end laptop = 4p
Original bill =18 × 4p + x × p = 72p + xp = (72 + x)p
Bill after mistake (laptops and desktops interchanged) = x × 4p + 18 × p = (4x + 18)p
New bill is 100% more → New bill = 2 × Original bill
So, (4x + 18)p = 2(72 + x)p
⇒ 4x + 18 = 144 + 2x
⇒ 2x = 126
⇒ x = 63
Ratio of laptops to desktops initially = 18 : 63 = 2 : 7