## anonymous one year ago How do you do 1.5/2.5 of 15?

1. phi

"of" means multiply $\frac{1.5}{2.5} \cdot 15$ to get rid of the decimals, you can multiply top and bottom by 10 $\frac{15}{25} \cdot 15$ can you finish?

2. phi

I would first simplify the fraction by dividing top and bottom by 5 what do you get ?

3. anonymous

like what is 1.5/2.5 of 15

4. phi

5. phi

do you know how to simplify 15/25 by dividing the top number by 5 and the bottom number by 5?

6. anonymous

you get 3/5

7. phi

yes, that means the problem is $\frac{3}{5} \cdot 15$ notice you can simplify more by dividing the bottom by 5 and the 15 (which is up top) by 5

8. anonymous

45/75

9. anonymous

The end answer is 9 but how do I get it?

10. phi

when you multiply fractions you multiply top times top and bottom times bottom if you have a whole number like 15, write it as 15/1 so it has a "bottom" but it is better to first simply first. you have $\frac{ 3}{5} \cdot \frac{15}{1} \\ \frac{3 \cdot 15}{5\cdot 1}$ I would not multiply 5*15 up top right away instead, divide the bottom by 5 and the top by 5 to get smaller numbers

11. anonymous

But im not multiplying

12. anonymous

Im trying to find out what is 1.5/2.5 out of 15

13. anonymous

and how to work it out

14. anonymous

15. anonymous

but how do I get it?

16. phi

English is confusing when describing math (which is why equations are easier to understand .. once you learn how) but you can get the idea this way: what is 1/2 of 2 ? notice the answer is 1. and 1/2 * 2 is also 1 It turns out the "of" means multiply

17. anonymous

Oh ok

18. phi

so try to simplify $\frac{3 \cdot 15}{5\cdot 1}$ by dividing top and bottom by 5

19. anonymous

3/3

20. anonymous

Cross multiply?

21. phi

in the bottom you have a 5. divide by 5 you get 1 up top you have a 15 what is 15/5 ?

22. phi

Once you learn the idea you will be able to do these problems

23. anonymous

3

24. phi

what we did was simplify $\frac{3 \cdot 15}{5\cdot 1} = \frac{3 \cdot 3}{1\cdot 1}$ now you can do the multiply and divide and get a simple number.

25. anonymous

im so confused

26. anonymous

How you get a one

27. phi

you could have done $\frac{3 \cdot 15}{5\cdot 1} = \frac{45}{5}$ and simplify to get 9 but it's easier for me to divide the 5 into the 15 right away

28. phi

if you have $\frac{15}{5}$ you can divide the top by 5 and the bottom by 5 to get $\frac{3}{1}$

29. anonymous

Thats easier for me. Thank you

30. phi

maybe. but notice if you had $\frac{256}{32}$ and no calculator. It should be clear you can divide top and bottom by 2 so you could simplify the problem to $\frac{128}{16}$ and then divide top and bottom by 2 again $\frac{64}{8}$ and now you might notice 64/8 is 8

31. phi

but if you did not notice 64/8 is 8 you could simplify by dividing top and bottom by 2 to get 32/4 and then 16/2 and then 8/1 or just 8