2006-12-17 14:35:59 · 10 answers · asked by shawntabulter 1 in Science & Mathematics ➔ Mathematics
15
2006-12-17 14:39:44 · answer #1 · answered by stwad 1 · 1⤊ 0⤋
15
2006-12-17 22:40:00 · answer #2 · answered by wild_turkey_willie 5 · 1⤊ 0⤋
21/x=7/5 then x=21*5/7, x=3*5=15. OK?
2006-12-18 05:58:02 · answer #3 · answered by Grasu M 2 · 0⤊ 0⤋
Proportions can be solved using cross-products, that is multiplying the numbers diagnal from each other.
The 21 and 5 get multiplied together which is 105 and the 7 and the x get multiplied which gives you 7x
So, 105=7x
Divide by 7 and you get 15=x
2006-12-17 22:50:51 · answer #4 · answered by Mathman90 2 · 1⤊ 0⤋
Cross multiply:
7*x=21*5
7x=105
Divide 7 from both sides:
x=15
Check:
21/15=7/5
7/5=7/5
2006-12-17 22:51:50 · answer #5 · answered by Anonymous · 0⤊ 0⤋
to solve proportions, cross multipy then divide
EXAMPLE---> 21/x = 7/5
to solve: 21 x 5 divided by 7
the answer is 15
2006-12-17 22:42:42 · answer #6 · answered by Mrs. Ben Dover 2 · 1⤊ 0⤋
x=15
2006-12-17 22:40:55 · answer #7 · answered by patient X 3 · 1⤊ 0⤋
First: get rid of fractions by taking the denominators and multiplying them by everything:
5x(21/x) = 5x(7/5)
Second: cross cancel like terms and multiply 5 and 21
5(21) = 7x
105 = 7x
Third: divide 7 by both sides:
105/7 = 7x/7
15 = x; x = 15
2006-12-17 22:42:47 · answer #8 · answered by ♪♥Annie♥♪ 6 · 1⤊ 0⤋
21/x = 7/5
x/21=5/7
x=5*21/7=5*3=15
2006-12-17 22:39:56 · answer #9 · answered by yupchagee 7 · 1⤊ 0⤋
21/x=7/5
21X1/x=7/5
1/x=7/5X1/21
1/x=1/15
x=15
2006-12-17 22:46:56 · answer #10 · answered by sam 3 · 1⤊ 0⤋