SOLUTION: A man is now five times as old as his daughter and five years ago the product of their ages was 105. Find their present ages.

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Question 1108990: A man is now five times as old as his daughter and five years ago the product of their ages was 105. Find their present ages.
Answer by ikleyn(52798) About Me  (Show Source):
You can put this solution on YOUR website!
.
M = 5*D               (1)
(M-5)*(D-5) = 105     (2)


Substitute (1) into (2):

(5D-5)*(D-5) = 105

(D-1)*(D-5)  =  21

D^2 -D - 5D + 5 = 21

D^2 - 6D - 16 = 0

(D+2)*(D-8) = 0.


The positive root D= 8 is the only meaningful solution.


Answer.  Daughter is 8 years old.  Father is 40 years old.

Solved.
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There is a bunch of lessons on age word problems
    - Age problems and their solutions
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    - Really intricate age word problem
    - Selected age word problems from the archive
    - Age problems for mental solution
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    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Age word problems".


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