How Old Did This Man Live to Be?
Date: 02/23/98 at 20:57:54 From: Christine Maruna Subject: Math I am trying to find the age of this person: he spent 3/13 of his life at school, 4/39 of his life in medical school, 1/2 his life as a surgeon, and he died 13 years into retirement. How old did he live to be? I don't know where to begin this problem. Thank you.
Date: 02/27/98 at 10:03:53 From: Doctor Jen Subject: Re: Math Hi there, I'd start by saying that ALL the parts of his life add up to 1. So you know that 3/13 + 4/39 + 1/2 + R = 1, where R is the fraction of his life he spent in retirement. We want to find the fraction that his retirement represents, because we know how many years his retirement lasted. So if we know that fraction, we can work out how long his total life was. Let's rearrange the equation to work out R. Take the fraction terms on the left side over to the right side: This gives us R = 1 - 1/2 - 4/39 - 3/13. Now we need to add the terms on the right side to find R. Are you okay with adding fractions? I'd imagine you are, if you're being asked questions like this. We know the length of his retirement was 13 years, and we know that 13 years represents R of his life: R*L, if L is the length of his life. You can use that information to work out just how long his life was. R*L = 13, and you know R, so L = ? Good luck... -Doctor Jen, The Math Forum Check out our web site http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.