.
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
- A fresh formulation of a traditional age problem
- Really intricate age word problem
- Selected age word problems from the archive
- Age problems for mental solution
in this site.
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Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Age word problems".
Save the link to this online textbook together with its description
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