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 November 3rd, 2018, 03:17 AM #1 Senior Member   Joined: Aug 2014 From: India Posts: 343 Thanks: 1 Why is my solution wrong? Meena purchased two fans each at Rs 1200. She sold one fan at the loss of 5% and other at the gain of 10%. Find the total gain or loss percent. Solution: C.P of first fans = 1200, Loss of first fan = 5% S.P of first fan = ((100-L% )/100)*C.P → S.P = ((100-5% )/100)*1200 → S.P = (95%)/100*1200 → S.P = 1140 C.P of second fan = 1200, gain of second fan = 10% → S.P = ((100 +10% )/100)*1200 → S.P = ((110% )/100)*1200 → S.P = 1320 Total S.P → 1140 + 1320 = 2460 Total C.P → 1200 + 1200 = 2400 Profit% = (S.P-C.P )/100 = (2460-2400)/100 = 60/100 = 60% But answer is 2.5%. Please tell where did I done wrong?
 November 3rd, 2018, 07:19 AM #2 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,470 Thanks: 949 1200 - 05% = 1140 1200 + 10% = 1320 ----------------------- 2400 + 2.5% = 2460
November 3rd, 2018, 07:28 AM   #3
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Quote:
 Originally Posted by Ganesh Ujwal Profit% = (S.P - C.P )/100
That should be Profit% = ((S.P. - C.P.)/C.P.)*100%, which gives (60/2400)*100%, i.e. 2.5%.

November 6th, 2018, 03:20 AM   #4
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Quote:
 Originally Posted by skipjack That should be Profit% = ((S.P. - C.P.)/C.P.)*100%, which gives (60/2400)*100%, i.e. 2.5%.
Are you saying my formula is wrong?

November 6th, 2018, 06:22 AM   #5
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Quote:
 Originally Posted by Ganesh Ujwal Meena purchased two fans each at Rs 1200. She sold one fan at the loss of 5% and other at the gain of 10%. Find the total gain or loss percent. Solution: C.P of first fans = 1200, Loss of first fan = 5% S.P of first fan = ((100-L% )/100)*C.P → S.P = ((100-5% )/100)*1200 → S.P = (95%)/100*1200 → S.P = 1140 C.P of second fan = 1200, gain of second fan = 10% → S.P = ((100 +10% )/100)*1200 → S.P = ((110% )/100)*1200 → S.P = 1320 Total S.P → 1140 + 1320 = 2460 Total C.P → 1200 + 1200 = 2400 Profit% = (S.P-C.P )/100 = (2460-2400)/100 = 60/100 = 60% But answer is 2.5%. Please tell where did I done wrong?
Yes, your formula in the last line is wrong.

You should have divided by the cost price of 2400. Why in the world would you divide by 100?

$60 \div 2400 = 0.025.$

Now if you want to turn 0.025 into a percent, you multiply by 100.

$0.025 \times \dfrac{100\%}{1} = 2.5\%.$

Last edited by JeffM1; November 6th, 2018 at 06:26 AM.

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