solve for x..

[naisha_grace]

a) 1/2 = x/10
x= 1/2 (10)
x= 5
am i right?!

but the next solving equations, i dont know how to solve it.. i forgot already.. please help..

b) x/55 = 5/10


c) 45/63 = 10/x


d) 36/x = 5.4/2.4


e) 42/14.7 = x/7


f) x/15 = 2.7/3[/b]

 

[tkhunny]

a) 1/2 = x/10
x= 1/2 (10)
x= 5
am i right?!
b) x/55 = 5/10
c) 45/63 = 10/x
d) 36/x = 5.4/2.4
e) 42/14.7 = x/7
f) x/15 = 2.7/3[/b]

b), e), and f) are EXACTLY the same.

Perhaps this indicates you really didn't know what you were doing on your CORRECT sample problem.

1/2 = x/10

The idea is to solve for 'x'. This means to get 'x' alone, with NOTHING attached to it. Keep asking yourself:
1) What is attached to 'x'?
2) How is it attached?

The answer: "OK, use the inverse operation to remove it.

1/2 = x/10

1) What is attached to 'x'? 10.
2) How is it attached? Division.
The inverse operation of Division is multiplication.

(1/2)*10 = (x/10)*10
5 = x

Similarly:
b) x/55 = 5/10

1) What is attached to 'x'? 55.
2) How is it attached? Division.
The inverse operation of Division is multiplication.
(x/55)*55 = (5/10)*55
x = (1/2)*55 <== Some simplification going on, there.
x = 55/2


e) 42/14.7 = x/7
1) What is attached to 'x'? 7.
2) How is it attached? Division.
The inverse operation of Division is multiplication.
(42/14.7)*7 = (x/7)*7
20 = x <== You can use a calculator to get you through tough arithmetic.

You do f), show your work, and then we can move on to the other ones.

 

[tkhunny]

c) 45/63 = 10/x
x = 45/63 (10)
5/7 (10)
x = 3.5

f) x/15 = 2.7/3[/b]
x = 2.7/3 (15)
x = 13.5

f) is good.

c) You did not notice that 'x' was in the denominator. That's 10/x, not x/10.

Let's just learn to manipulate.

45/63 = 10/x

First, notice that x CANNOT be zero. Why is that?

Second, do look around for ways to simplify the problem. Common factors could be hanging around, inflating the numbers you have to track.

45/63 = (9*5)/(9*7) = (9/9)*(5/7) = 1*(5/7) = 5/7

Now we have:

5/7 = 10/x

Keep looking. Divide every term by 5.

(5/7)/5 = (10/x)/5
1/7 = 2/x

Well, that's WAY simpler.

A good goal, but not mandatory, is getting rid of fractions. Don't be afraid of fractions, just learn to get rid of them when you think it is the right thing to do.

If nothing else comes to mind, just multiply everything by every denominator.

1/7 = 2/x

Multiply by 7

7*(1/7) = 7*(2/x)
1 = 14/x

Multiply by 'x'

x*1 = x*(14/x)
x = 14

There, we weren't even trying to solve it. We were just getting rid of fractions and simplifying things. We solved it almost by accident.

OK, you do the last one. NO guessing.