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 June 30th, 2018, 10:15 PM #1 Senior Member   Joined: Aug 2014 From: India Posts: 458 Thanks: 1 How is this big formula obtained? A man bought 90 watches and marked a tag price 25% of the C.P He started to give 10% discount for the cash payment and 5% discount for others He sold 3/4 of the stock in cash payment. If he earned 2250 as a profit. Find the cost of each watch. Solution: X(5/4)(9/10)(30) + X(5/4)(19/20)(10) = 2250 How is this big formula obtained?
 June 30th, 2018, 10:42 PM #2 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Are you sure the man didn't buy 40 watches instead of 90?
June 30th, 2018, 10:50 PM   #3
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Quote:
 Originally Posted by MarkFL Are you sure the man didn't buy 40 watches instead of 90?
he's also forgotten to subtract out the initial cost of the watches

June 30th, 2018, 10:54 PM   #4
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Quote:
 Originally Posted by romsek he's also forgotten to subtract out the initial cost of the watches
Yes, my next question was going to be regarding whether revenue rather than profit was 2250.

 June 30th, 2018, 11:50 PM #5 Senior Member   Joined: Aug 2014 From: India Posts: 458 Thanks: 1 Oh sorry it is 40 watches
July 1st, 2018, 12:16 AM   #6
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Quote:
 Originally Posted by Ganesh Ujwal . . . a tag price 25% of the C.P.
I assume you meant "a tag price 25% in excess of the C.P." or words to that effect, which would make the tag price 5/4 times the C.P. (cost price). The equation seems to be using "X" for the cost price.

July 1st, 2018, 08:05 AM   #7
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Quote:
 Originally Posted by Ganesh Ujwal A man bought 40 watches and marked a tag price 25% of the C.P. He gave 10% discount for cash payment and 5% discount for others. He sold 3/4 of the stock in cash payment. If his net profit was 2250, find the C.P. of each watch. Solution: X(5/4)(9/10)(30) + X(5/4)(19/20)(10) = 2250
Ganesh, look at X(5/4)(9/10)(30):

5/4 = 1.25 (tag price = C.P. + 25%)
9/10 = .9 = 1 - .10 (cash payment price reduced by 10%)
30 = 3/4 * 40 (number sold as cash payment)

Do you understand that?

July 1st, 2018, 08:17 PM   #8
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Quote:
 Originally Posted by Denis Your problem reworded: Ganesh, look at X(5/4)(9/10)(30): 5/4 = 1.25 (tag price = C.P. + 25%) 9/10 = .9 = 1 - .10 (cash payment price reduced by 10%) 30 = 3/4 * 40 (number sold as cash payment) Do you understand that?
Why multiply all of them?

 July 1st, 2018, 09:56 PM #9 Global Moderator   Joined: Dec 2006 Posts: 20,929 Thanks: 2205 The multiplication by 5/4 to get the tag price is because that is equivalent to adding 25% to the CP. Similarly, the multiplication by 9/10 is because that is equivalent to giving a discount of 10% of the tag price. The multiplication by 30 is to give the total amount received for 30 watches that were sold at a 10% discount. These multiplications could be done in succession, but the result would be the same as the result of doing them all together.
July 2nd, 2018, 10:10 AM   #10
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Quote:
 Originally Posted by Ganesh Ujwal Solution: X(5/4)(9/10)(30) + X(5/4)(19/20)(10) = 2250
You also goofed up on the shown solution; should be:

X = cost price of 1 watch (ALWAYS declare your variables!)

X(5/4)(9/10)(30) + X(5/4)(19/20)(10) - 40X = 2250

Solve: X = 400

May we ask you to be more careful? Thank you.

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