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seropon [69]
3 years ago
5

If a varies directly as b, and a = 28 when b = 7, find b when a = 5.

Mathematics
2 answers:
maxonik [38]3 years ago
8 0

ANSWER

The correct choice is B.

EXPLANATION

If 'a' varies directly as 'b' then we write the equation of variation,

a = kb

Where k is the constant of variation.

We have that a = 28 when b = 7.

This implies that,

28= 7k

k = 4

The equation now becomes

a = 4b

When we a=5, we have

5 = 4b

b =  \frac{5}{4}

The correct answer is B

Reika [66]3 years ago
6 0

Answer: Option B.

b=\frac{5}{4}

Step-by-step explanation:

If a varies directly with b then when a increases b it also increases by a factor k.

Then we can write that

a = kb

We know that when a = 28 then b = 7. So

28 = k * 7

k=\frac{28}{7}

k=4

Therefore the equation of proportionality is:

a=4b

So when a=5  then:

5=4b\\\\b=\frac{5}{4}

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... a + b/c = (a×c/c) + b/c = (ac +b)/c

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