User Name Remember Me? Password

 Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

 June 15th, 2018, 09:15 PM #1 Senior Member   Joined: Aug 2014 From: India Posts: 470 Thanks: 1 How is this step obtained Kiran bought some goods for 720/- He sold one forth of the goods at a profit of 15% At what profit percentage should he sell the remaining goods to gain an overall profit of 21%? Solution: The amount of money Kiran wants to end up with is 720 * 1.21 = 871.2 He already sold one forth of it for which he made a profit of 15%. 720/4=180 and 180*1.15=207 So we need to find x so that (720-180)*x=871.2-207 --> 540x=664.2 --> x≈1.23 so he needs to sell the remaining goods at 23% profit. How is this step obtained: So we need to find x so that (720-180)*x=871.2-207 ? June 15th, 2018, 09:32 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 I think I'd use a weighted average here: $\displaystyle \frac{1}{4}\cdot1.15+\frac{3}{4}(1+x)=1.21$ Multiply through by 400: $\displaystyle 115+300(1+x)=484$ $\displaystyle 300(1+x)=369$ $\displaystyle 1+x=\frac{123}{100}$ $\displaystyle x=\frac{23}{100}=23\%$ Thanks from Ganesh Ujwal Last edited by MarkFL; June 15th, 2018 at 09:42 PM. June 15th, 2018, 09:35 PM   #3
Senior Member

Joined: Aug 2014
From: India

Posts: 470
Thanks: 1

Quote:
 Originally Posted by MarkFL I think I'd use a weighted average here. Multiply through by 400:
In what cases should I use "weighted average"?

why did you multiple with 400? June 15th, 2018, 09:41 PM   #4
Senior Member

Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

Posts: 12,211
Thanks: 521

Math Focus: Calculus/ODEs
Quote:
 Originally Posted by Ganesh Ujwal In what cases should I use "weighted average"? why did you multiple with 400?
A weighted average is "an average resulting from the multiplication of each component by a factor reflecting its importance."

Here we had 1/4 of an amount increased by 15% and the remaining 3/4 increased by an unknown percentage, and we require that the overall increase be 21%. So, this is a good time to apply a weighted average.

I multiplied by 400 to get rid of the denominators in the fractions and to make the decimal values integers. The denominators are 4and the decimal values have 2 places, so a factor of 400 will do both at the same time. June 15th, 2018, 09:50 PM #5 Senior Member   Joined: Aug 2014 From: India Posts: 470 Thanks: 1 Why 1+X instead of Just X? June 15th, 2018, 10:02 PM #6 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs I wanted just the percentage increase. If you are going to increase an amount by 25%, you would multiply that amount by: 1 + .25 = 1.25 Suppose we wish to increase the quantity r by 25%, we would want to take r and add 25% or r: r + .25r = r(1 + .25) = 1.25r In the equation I posted, I wanted x to represent just the increase.  June 15th, 2018, 10:03 PM #7 Newbie   Joined: Jun 2018 From: USA Posts: 2 Thanks: 0 Kiran should get 871.2 to get final profit percent of 21% by selling 1/4 at 15% profit, he got 207. So he should get (871.2-207=664.2) by selling the other 3/4 part. Initial price of 3/4 part is (720-180). So if x is the multiplying factor including the increase percentage(for 15% increase, the factor is 1+0.15=1.15) (720-180)*x=871.2-207 x=1.23 so he should sell the 3/4 part at 23% profit. June 16th, 2018, 02:13 AM #8 Global Moderator   Joined: Dec 2006 Posts: 20,978 Thanks: 2229 x = (871.2 - 207)/(720 - 180) = 664.2/540 = 110.7/90 = 1.23 June 16th, 2018, 04:20 AM   #9
Senior Member

Joined: Aug 2014
From: India

Posts: 470
Thanks: 1

Quote:
 Originally Posted by skipjack x = (871.2 - 207)/(720 - 180)
What formula have you used? June 16th, 2018, 08:54 AM #10 Global Moderator   Joined: Dec 2006 Posts: 20,978 Thanks: 2229 I used profit on 3/4 of the goods = overall profit - profit on 1/4 of the goods, then I evaluated the numerator and denominator separately and used 540 = 6*90 to allow the division to be done by dividing first by 6 and then by 90. Tags obtained, step Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post Ganesh Ujwal Elementary Math 9 May 3rd, 2018 09:26 AM Ganesh Ujwal Elementary Math 1 April 19th, 2018 01:09 AM dalo Math Software 1 March 17th, 2013 10:19 PM mathLover Algebra 4 April 17th, 2012 02:02 AM Weiler Differential Equations 1 January 31st, 2012 07:15 AM

 Contact - Home - Forums - Cryptocurrency Forum - Top       