Question

The cost of an I-pad increases by 10% and the cost of a mobile increases by 18%. The cost of an I-pad is thrice the cost of a mobile. Find the percentage increase in the total cost of 10 I-pads and 5 mobiles.

• A. 10%
• B. 11.14%
• C. 14.63%
• D. 18%

Hint:

Let the mobile's price be a variable, write the I-pad's price as three times that, then compare the total cost before and after the price rise.

Answer 1

The Correct Option is B

Step 1: Assume concrete values instead of a variable.
Assume the mobile costs $100.
Since the I-pad costs three times as much as the mobile, the I-pad costs $300.

Step 2: Work out the original bill.
10 I-pads cost $10 \times 300 = 3000$.
5 mobiles cost $5 \times 100 = 500$.
The total original bill is $3000 + 500 = 3500$.

Step 3: Work out the new bill.
I-pads go up by 10 percent, so 10 I-pads now cost $3000 \times \frac{110}{100} = 3300$.
Mobiles go up by 18 percent, so 5 mobiles now cost $500 \times \frac{118}{100} = 590$.
The total new bill is $3300 + 590 = 3890$.

Step 4: Compute the percentage rise.
The rise in the bill is $3890 - 3500 = 390$.
The percentage rise is \[ \frac{390}{3500} \times 100 = 11.142857...\% \approx 11.14\% \]
This sits closer to the I-pad's own 10 percent rise than to the mobile's 18 percent rise, because I-pads make up the bigger share of the total spend.

Final Answer:
The combined cost of the 10 I-pads and 5 mobiles rises by close to 11.14 percent. \[ \boxed{11.14\%} \]