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I'm having trouble setting up these kind of math questions:
Sally is 4/5 as old as her sister Jane. Their brother Dick's age is 1/3 more than Jane's. If Dick is 20, how old is Sally?
Know here is the explanation from kaplan....
This is a relatively easy problem. You just have to be careful when you set up your equations. Let's
let S be Sally's age, in years, J be Jane's age, in years, and D be Dick's age, in years. We know that Sally
is
4
5
as old as Jane, thus S = 4/5
J . We know that Dick's age is1/3
more than Jane's age, thus Dick's age is 4/3
times Jane's age or D = 4/3j
J . We are given that Dick's age is 20. We have 20 = 4/3
J . To get J, we
multiply both sides of this equation by3/4
, so J = 3/4
D = 3
4
(20) = 3 × 5 = 15, therefore Jane is 15 years old.
Now we want to find Sally's age. We know that S = 4
5
J meaning that Sally's age is
4
5
of Jane's age. We
know that Jane's age is 15, therefore Sally's age is
4
5
of 15, or 12. Sally's age is 12 and that is answer
choice C.
The part im stuck at is when they say We know that Dick's age is1/3
more than Jane's age, thus Dick's age is 4/3
times Jane's age or D = 4/3j
How do you get D= 1/3 + J (i don't know if this set up is even right) to D=4/3J?
Sally is 4/5 as old as her sister Jane. Their brother Dick's age is 1/3 more than Jane's. If Dick is 20, how old is Sally?
Know here is the explanation from kaplan....
This is a relatively easy problem. You just have to be careful when you set up your equations. Let's
let S be Sally's age, in years, J be Jane's age, in years, and D be Dick's age, in years. We know that Sally
is
4
5
as old as Jane, thus S = 4/5
J . We know that Dick's age is1/3
more than Jane's age, thus Dick's age is 4/3
times Jane's age or D = 4/3j
J . We are given that Dick's age is 20. We have 20 = 4/3
J . To get J, we
multiply both sides of this equation by3/4
, so J = 3/4
D = 3
4
(20) = 3 × 5 = 15, therefore Jane is 15 years old.
Now we want to find Sally's age. We know that S = 4
5
J meaning that Sally's age is
4
5
of Jane's age. We
know that Jane's age is 15, therefore Sally's age is
4
5
of 15, or 12. Sally's age is 12 and that is answer
choice C.
The part im stuck at is when they say We know that Dick's age is1/3
more than Jane's age, thus Dick's age is 4/3
times Jane's age or D = 4/3j
How do you get D= 1/3 + J (i don't know if this set up is even right) to D=4/3J?