Maths Question

2007-12-22 7:54 pm

( a + 2 ) : ( a + 5 ) : b = 3 : 4 : 7

Find the value of a and b .

Thank you !!

{Ratio and Rate}

回答 (2)

2007-12-22 8:03 pm

✔ 最佳答案

唔洗睇b住..
睇( a + 2 ) : ( a + 5 ) = 3 : 4
4(a+2)=3(a+5)
4a+8=3a+15
4a-3a=15-8
a=7
( a + 5 ) : b = 4 : 7
12x7=4b
b=84/4
b=21

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2007-12-22 8:10 pm

Find a
a+2/a+5=3:4
a+2/a+5=3/4
4a+8=3a-4a
-15+8=-a
-7=-a
7=a
a=7
Find b
(a(7)+2):(a(7)+5):b=3:4:7
9:12:b=3:4:7
12/b=4/7
84=4b
b=21

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