A boy is 4 years old and his sister is three times as old as he is. When the boy is 12 years old, how old w?

Answer 1

In the real world she would be 20.
4x3=12 ,
4+8=12,
12+8=20.
That is relevant math as we understand it and as we agree on.
It could be boy is 4 and sister is 3 times older, mathematically
4x3=12
12x3=36
One can complicate or clarify anything with math, when it is agreed upon.

.

Answer 2

Sister's age = 3*4 = 12 years
When the boy is 12 years means after (12-4=)8 years, sister's age would be 12+8
=20 years

Answer 3

Boy is 4 yeas old and sister is 3 times as old, that is 12 years. When boy reaches 12 years, sister will be 12 + (12 - 4) = 12 + 8 = 20 years old.

Answer 4

Real life tells us that age moves at a slope of 1 (The sister's age S increases 1 for every 1 increase in the boy's age B). Our first ordered pair is (4, 3*4) or (4, 12). Since we have a point and a slope, we can find an equation for the line using the point-slope form:
y-y1 = m(x-x1)
S-12 = 1(B-4)
S = (B-4) + 12
S = B + 8
Now that we have a relationship between the numbers, we can plug in the variable for the question:
S = 12 + 8
S = 20.

Yes, this is the long way of doing it: most people do the middle steps without thinking about them or writing them out. But I've always found that if you know *how* it fits together, you'll be able to figure it out easier next time.

Answer 5

Boy 4 sister 3 x 4 = 12
In 8 years boy 12 and sister 20.

Answer 6

In Present:
the boy's age = 4 yrs old
his sister's age = 4 times 3 = 12

8 years hence:
boy's age = 4 + 8 = 12
his sister's age = 12 + 8 = 20

Answer 7

20

Answer 8

Boy's present age = 4 yrs.
Sister's present age = 4*3 = 12 yrs

After 8 yrs.,
Boy's age = 12 yrs.
Sister's age = 12 + 8 = 20 yrs. Answer

Answer 9

20

Answer 10

20