# direct variation

If y=36 when x =6 find x when y = 42
If y=-18 when x=6 find x when y=6
If y =12 when x= 15 find x when y =21
If y=-6.6 when x=9.9 find y when x =6.6
If y=6 when x=(2/3)find x when y=12

those are the problems you don't have to do all just at least show me step by step how you arrived at the answer thank you so much for helping

take the first one:

y1/y2 = x1/x2

y1=36 x1 is 6
y2=42 x2 is ?
then
36/42=6/x solve for x
and
x=42*6/36 =7

check my thinking.

hyng bbncnnh gbgbn

These are proportion problems
(1) 6:36=x:42 Which is the same as (6*42)/36=x
(2)6:18=x:6 Which is the same as (6*6)/18=x
(3) 15:12=x:21 I think you can do them now
(4)9.9:-6.6=6.6:y Watch where the y is located here.
(5)(2/3):6=x:12 Be sure to handle the fraction correctly.

In general, a proportion is two ratios a:b=c:d
a and d are called the extremes and b and c the means.
The fundamental relation is a*d=b*c The product of the extremes = the product of the means.
You can also think of it in terms of fractions a/b = c/d. in terms of fractions both ratios are different names for the same fraction. One is a multiple of the other. In the first one we have
6:36 or 6/36=1/6
We want to find x such that x/42 = 1/6 so x=42*(1/6)
You can verify that 1/6 = 6/36 = 7/42.
The fraction 1/6 would be the fraction in lowest terms in integers. In some places finding that lowest reducible integer fraction is very important. Other times we can't find such an integer ratio, e.g. if the numbers are irrational.

If y =12 when x= 15 find x when y =21

y=kx 21

1. 👍
2. 👎
3. 👁

## Similar Questions

1. ### Algebra II

Solve x^4 - 12x - 5 = 0 given that -1 + 2i is a root. I’ve used synthetic division to get the answers x = 1 +/- 2i , 1 +/- sqrt 2 I’ve having trouble checking the answers though because of that imaginary number. How can I

2. ### math

A student missed 71 problems on a biology test and received a grade of 22%. If all the problems were of equal value, how many problems were on the test? Follow the problem-solving process and round your answer to the nearest

3. ### Math (Trig Review)

Evaluate the expression without using a calculator (Make a sketch of a right triangle) tan(arccot 2) Thanks in advance! I'm trying to refresh my memory of these kinds of problems and I'm having trouble on how to solve this problem

4. ### math

5) A student answered 86 problems on a test correctly and received a grade of 98%. How many problems were on the test, if all the problems were worth the same number of points?

1. ### Math

Kenneth has 22 math problems to do for homework. He has 12 problems done.How many more problems does he left?if he completes 1 problem every minute,how many more minutes does he have to work?

2. ### algebra

A student missed 11 problems on a Chemistry test and received a grade of 65%. If all the problems were of equal value, how many problems were on the test? Round off your answer to the nearest integer. X= # of problems 11= 3 of

3. ### Math

The coordinates of the end-points of a line segment PQ are P(3,7) and Q(11,-6). Find the coordinates of the point R on the y-axis such that PR = QR. Please include the workings, as I would like to be able to perform these problems

4. ### Science-Physics

The metre was originally defined as a fraction of the distance from the North Pole to the equator. What problems would this definition of the metre create for people? Would some problems be the long calculation? I can't really

1. ### Math 8R - help!!!!!!!!!!!!!

Multi-Step Equations Solving Equations with Variables on Both Sides 1) 5y + 4 = 4y + 5 11a + 9 = 4a + 30 2w + 3 = 4w - 5 2) 3a - 10 = 4 + a 2x - 1 = x - 3 6n + 4 = n - 11 3) 29r + 4 = 28 + 13r 7x - 11 = -19 + 3x 4) b + 3 = 2b - 7

2. ### algebra homework help

student missed 11 problems on a Chemistry test and received a grade of 65%. If all the problems were of equal value, how many problems were on the test? Round off your answer to the nearest integer. X= # of problems 11= # of

3. ### math

So I've been having trouble solving some problems. Mainly problems that look like this 5-(t+3)=-1+2(t-3) what causes problems is the 5- part. I asked my teacher for help, and he gave me a hint, which is to distribute a -1 like

4. ### Calculus

I am having a lot of trouble doing these types of problems. Can someone show me how to do this. Thank you for your time. Evaluate the definite integral 4 x(x+3)dx 0