Mark is 11 years older than his sister. In 8 years he will be twice as old as she will be then. How old are they now?
M = S+11
M+8 = 2*(S+8) = 2*S + 16
Now solve
M = 2S+8
2S+8 = S+11
S = 3
M = 14
T=25+R
R=25-5=20
20+25=45
T=45
R=20
Bob is 8 years older than his sister. 3 years ago he was 3 times older than his sister. How old are they both?
To solve this problem, let's assign variables to the ages of Mark and his sister. Let's say Mark's age is represented by "M" and his sister's age is represented by "S". We are given two pieces of information:
1. Mark is 11 years older than his sister: M = S + 11
2. In 8 years, Mark will be twice as old as his sister will be then: M + 8 = 2*(S + 8)
Now, we can use these two equations to solve for their current ages. Let's substitute the value of M from the first equation into the second equation:
(S + 11) + 8 = 2*(S + 8)
Simplifying the equation:
S + 19 = 2S + 16
Subtracting S from both sides:
19 = S + 16
Subtracting 16 from both sides:
3 = S
Now we know that the sister is 3 years old. We can substitute this value back into the first equation to find Mark's age:
M = S + 11
M = 3 + 11
M = 14
Therefore, Mark is 14 years old and his sister is 3 years old.