Question

The fourth proportional to 3, 5, 9 is
1. 12
2. 14
3. 15
4. 20

Answer 1

Answer:

15 because , 3,5,9 a/b=c/d

3/5=9/x

3×x=9×5

x=9×5/3

3×1=3

3×3=9

3×5 = 15

Answer 2

Solution :-

we know that,

• fourth proportional of a , b and c is d when a : b = c : d or, a/b = c/d or, ad = bc .

So, let fourth proportional of 3, 5 and 9 is x .

then,

→ 3 : 5 :: 9 : x

→ 3 : 5 = 9 : x

→ (3/5) = (9/x)

→ 3 * x = 9 * 5

→ x = 3 * 5

→ x = 15 (3) (Ans.)

therefore , fourth proportional to 3 , 5 , 9 is 15 .

Learn more :-

let a and b positive integers such that 90 less than a+b less than 99 and 0.9 less than a/b less than 0.91. Find ab/46

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