Father is twice as old as son, and daughter is twice as young as mother?

Question

If mother is four years younger than the father, by how many years sister is younger than her brother?

Answer 1

2s=f
m+4=f
2d=m

2s=m+4
2s=2d+4
s=d+2

Sister is 2 years younger than the brother

Answer 2

2

Answer 3

2

Answer 4

2 years

here's how you figure it out. pick an age for the son. Any age, doesn't matter. I'll say....20. Okay, father is twice as old, so dad is 40. Mom is 4 years younger than dad, so mom is 36. Daughter is twice as young as mom (or half her age), so daughter is 18, which is 2 years younger than brother.

Answer 5

Let S be the age of the son, F the father, M the mother, D the daughter. We seek S-D.

The conditions give the following system of simultaneous equations:

1. F=2S
2. M=2D
3. F=M+4

Substitute from 1. and 2. into 3. to obtain:

2S = 2D + 4.

Divide throughout by 2:

S=D + 2

Thus S-D = 2, so the answer is 2 years

Answer 6

F : (1/2)F= S
M : (1/2)M = D

assume the mother is 36;
36+4 = Father = 40
daughter = 36/2 = 18
son = 40/2 = 20
20 - 18 = 2

ANS:2

Answer 7

If you can't handle the math, just use an example.

If Father is 20 then Son is 10

If Father is 20 then Mother is 16

If Mother is 16 then daughter is 8 (assuming "twice as young" means "half as old")

Difference between Son and Daughter is 2

You can try your own examples, to verify it.

Answer 8

4

Answer 9

4

Answer 10

2, I think

If dad is 22, son is 11
22-4 = 18 , mom's age. 1/2 of 18 is 9.

If son is 11, daughter is 9, 2 years difference. I've thrown other numbers into my equation and it balances for me.

Answer 11

2 years younger.