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# If f(x, y) = x2y and f(a, b) = 6, what is f(2a, 4b)?

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If f(x, y) = x2y and f(a, b) = 6, what is f(2a, 4b)? [#permalink]  30 Jul 2018, 10:13
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Question Stats:

85% (00:41) correct 14% (01:40) wrong based on 14 sessions
If $$f(x, y) = x^2y$$and $$f(a, b) = 6$$, what is $$f(2a, 4b)$$?

[Reveal] Spoiler: OA
96

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Sandy
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Manager
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Re: If f(x, y) = x2y and f(a, b) = 6, what is f(2a, 4b)? [#permalink]  05 Aug 2018, 17:09
Manager
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Re: If f(x, y) = x2y and f(a, b) = 6, what is f(2a, 4b)? [#permalink]  06 Aug 2018, 20:44
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kruttikaaggarwal wrote:

Sure thing.

The equations we are given is that $$f(x,y) = x^2 y$$ and $$f(a,b) = 6$$ in order to find out $$f(2a,4b)$$.

Using the first equation, we can change $$f(2a,4b)$$ into another form. $$(2a)^2 * 4b$$

$$(2a)^2 * 4b$$

$$4 * a^2 * 4 * b$$

$$16 * a^2 b$$ (does this $$a^2 b$$ look familiar? it's the second equation we were given, so we can substitute this value for 6)

$$16 * 6 = 96$$

Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 175

Kudos [?]: 3028 [1] , given: 394

Re: If f(x, y) = x2y and f(a, b) = 6, what is f(2a, 4b)? [#permalink]  12 Aug 2018, 07:00
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Expert's post
Explanation

The problem provides the function $$f(x, y) = x^2y$$ and also the fact that when a and b are plugged in for x and y, the answer is 6. In other words:

$$f(x, y) = x^2y$$

$$f(a, b) = a^2b = 6$$

The problem asks for the value of f(2a,4b). First, plug 2a in for x and 4b in for y:

$$f(2a, 4b) = (2a)^2(4b)$$

$$f(2a, 4b) = 4a^2(4b)$$

$$f(2a, 4b) = 16a^2b$$

The problem already provides the value for the variables: a2b = 6. Therefore, $$16a^2b = 16(6) = 96$$.
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Re: If f(x, y) = x2y and f(a, b) = 6, what is f(2a, 4b)?   [#permalink] 12 Aug 2018, 07:00
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