# Math Help - 2 problems

1. ## 2 problems

Alright well basically I've got 2 problems, haven't done algebra in a year, totally forgot how to do this stuff.

√x/y =4 , which of the following represents y in terms of x?

a. y = x/2

b. y = 2/x

c. y = x/16

d. y = 16/x

problem number 2

The forumla P = 2pi (√L/32) can be used to approximate the period of a pendulum,

Where L is the pendulum's length in feet and P is the pendulum's period in seconds. If a pendulum's period is 1.6 seconds, what is the length of the pendulum to 3 decimal places?

2. ## Re: 2 problems

I'll get you started on the answer to the first problem:

IF:

√(x/y) = 4

THEN:

x/y = 4*4 = 16, so:

x = 16y

can you continue?

3. ## Re: 2 problems

Please use parentheses. What you wrote is this:

$\frac {\sqrt{x}}y = 4$

but I think what you meant is this:

$\sqrt{\frac x y } = 4$

It makes a difference. Same with the second problem - the correct formula is $P = 2 \pi \sqrt{ \frac L {32}}$, not $P = 2 \pi \frac {\sqrt{ L}} {32}$

In both cases you can start by squaring both sides of the equation and then rearranging. For problem 1 to get 'y' as the subject after squaring you will want to multiply both sides of the equation by y, then divide both sides by 4^2. For problem 2 to get L as the subject after squaring both sides you can divide both sides by 2pi and then multiply both sides by 32. Try it and post back with the results you get.

4. ## Re: 2 problems

So is y 16/x?

5. ## Re: 2 problems

Let's try your answer and see if it works. If y = 16/x then starting with original equation:

$\sqrt{\frac x y } = 4$, substitue 16/x for y:

$\sqrt {\frac {x}{16/x}} = 4$. Now group the x terms:

$\sqrt { \frac {x^2}{16}} = 4$. And take the square root of both sides:

$\frac x 4 = 4$

So no, it doesn't seem to work. Starting with what Deveno left you with: x=16y, what happens if you divide both sides by 16?

6. ## Re: 2 problems

For the first problem y=16/x

and for the second problem here is what your going do:
P = 2pi(√L/32)
√(L/32) = P/2pi
√L = P√32/2pi
L = (32P^2)/(4pi^2)

after this you do the calculations and you get L = 2.075