Question 1012058: In 1950 Roberto was four times as old as Juan. In 1955 Roberto was three times as old as Juan. How old was Roberto when Juan was born?
Found 3 solutions by ikleyn, macston, MathTherapy:
Answer by ikleyn(52795)   (Show Source):
You can put this solution on YOUR website! .
In 1950 Roberto was four times as old as Juan. In 1955 Roberto was three times as old as Juan. How old was Roberto when Juan was born?
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In 1950: R = 4*J (1)
where R is Roberto's age in 1950, and J is Juan's age in 1950, at the moment of comparison.
In 1955, 5 years later:
R + 5 = 3*(J + 5). (2)
Solve these two equations. Substitute (1) into (2) and simplify.
4J + 5 = 3J + 15,
J = 15 - 5 = 10.
So, in 1950 Juan was 10 years old. Roberto was 40 years old in 1950.
Thus Roberto is 30 years older than Juan.
Hence, Roberto was 30 years old when Juan was born.
Answer by macston(5194)  (Show Source):
You can put this solution on YOUR website! .
R=Roberto's age in 1950; J=Juan's age in 1950
.
R=4J
.
R+5=3(J+5)
4J+5=3J+15
J=10
Juan was 10 in 1950.
.
R=4J=4(10)=40
Robert was 40 in 1950
.
40-10=30
ANSWER: Robert was 30 when Juan was born
Answer by MathTherapy(10552)  (Show Source):
You can put this solution on YOUR website!
In 1950 Roberto was four times as old as Juan. In 1955 Roberto was three times as old as Juan. How old was Roberto when Juan was born?
Let Juan’s age, in 1950 be J
Then Roberto’s age, in 1950 was 4J
Therefore, difference in ages = 4J – J, or 3J
In 1955, Juan was J + 5, and Roberto was: 4J + 5
We then get: 4J + 5 = 3(J + 5)
4J + 5 = 3J + 15
4J – 3J = 15 – 5
J, or Juan’s age, in 1950, was: 10
Roberto’s age, in 1940, when Juan was born, was 3(10), or 
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