SOLUTION: if a:b = 4:5 and a:(b+c)= 3:7 then a:c is a) 1:2 b) 2:5 c) 4:7 d) 12:13 e) 20:21

Question 237580: if a:b = 4:5 and a:(b+c)= 3:7 then a:c is
a) 1:2 b) 2:5 c) 4:7 d) 12:13 e) 20:21

Answer by nyc_function(2741) (Show Source): You can put this solution on YOUR website!
Let a = 4
Let b = 5
Then we can make:
4/(5 + c) = 3/7
Cross-multiply:
3(5 + c) = 4(7)
15 + 3c = 28
3c = 28 - 15
3c = 13
c = 13/3
We are looking for a:c, which is really a/c.
We know a and we just found b.
So, plug and chug.
4/(13/3) = 12/13 = 12:13
Answer is choice d.
===============================
By the way, a:b can also be written a to c, which can also be written as a/c.
They all mean the same thing.
===============================

Think about it this way:
Batman:Robin = Batman to Robin = Batman/Robin

RELATED QUESTIONS
3 1/2+ 4 3/4+ 5 3/10 (a)12 7/16 (b)13 11/20 (c)16/33 (d)12 9/80 (e)none of these (answered by Alan3354)

3 1/2+ 4 3/4+ 5 3/10 (a)12 7/16 (b)13 11/20 (c)16/33 (d)12 9/80 (e)none of these (answered by Edwin McCravy)

If a:b=9:4, and b:c=5:3, then (a-b) : (b-c) is equal to A. 7:12 B. 25:8 C. 4:1... (answered by stanbon)

http://tinyurl.com/8jd66mb Please check my answers, and fill in the ones I skipped.... (answered by swincher4391)

{{{(2/3)/(5/4)of(20/21)}}}=? (A)7/8 (B)1/3 (C)32/63 (D)... (answered by ewatrrr)

If a is a solution of the equation: 7/4+(1/5)x-3/2=(4/5)x, then 12a+5= A) 5/3 B)... (answered by fractalier)

1) a=6 b=8 c=? 2) a=? b=12 c=13 3) a=? b=4 c=5 4) 9 21 ? 5) 24 10 ? 6) ? 3 4 (answered by Edwin McCravy,richwmiller)

a:b=2:5 and a:c=3:7. What is c:b? A. 5:7 B. 14:15 C. 2:7 D. 15:14 E.... (answered by MathLover1,Edwin McCravy,greenestamps,ikleyn,josgarithmetic)

Simplify: 30/12 a. 30/12 b. 5/2 c. 10/3 d. 10/4 e. 7/3 Simplify: 13/39 a. 3 b. 13/39 (answered by jessica43)