If a varies directly as b, and a = 28 when b = 7, find b when a = 5.
2 answers:
ANSWER
The correct choice is B.
EXPLANATION
If 'a' varies directly as 'b' then we write the equation of variation,

Where k is the constant of variation.
We have that a = 28 when b = 7.
This implies that,


The equation now becomes

When we a=5, we have


The correct answer is B
Answer: Option B.

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

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



Therefore the equation of proportionality is:

So when
then:

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