Posted by **Anonymous** on Wednesday, November 14, 2007 at 1:24pm.

Can someone help me with this problem? multiply and simplify 4 1/5 x 10/21 x 9/20. I know after you simplify 4 1/5 it will be 21/5. What is the next step.

- math -
**Phillip**, Wednesday, November 14, 2007 at 3:38pm
21/5 x 10/21 x 9/20. You can multiply all the numerators (top numbers) and then all the denominators (bottom numbers), then simplify. However,it is much easier to simplify before multiplying. To do this, find a number that will divide evenly into any numerator and any denominator. There is a 21 for a num. and a 21 for a den. so 21/21 = 1. Now you have 1/5 x 10/1 x 9/20. You have a 5 in a den and a 10 in a num so you could divide out the common 5 which is 1/1 x 2/1 x9/20.( Or you could look at the num 10 and the den 20 - dividing out the common 10. It does not matter which num and den you use as long as they have a common factor and are not both num or both den.)In 1/1 x 2/1 x 9/20, there is a common factor of 2 that can be divided into the num 2 and the den 20 leaving 1/1 x 1/1 x 9/10. Now multiplying all num then all den gives you 9/10. This is much easier to see when you write it on paper. If you don't understand let me know

## Answer this Question

## Related Questions

- Algebra - Can someone please help me with math problem and explain to me step by...
- Math - I'm studying to take a math placement exam and it has been a long time ...
- algebra - Solve. x/9-1/7=26/63 STEP 1: The LCM is _________ To clear ...
- math - how do i do x2+12x+32 x2+12x = 14x+32 subtract 14x from each side 14x=32 ...
- Algebra - I having a hard time with this word problem: A backyard has dimensions...
- MATH - How do you write fractions in simplest form? for example I need ...
- Math - Multiply and simplify. 9y^6/10t^4*100t^8/81y. I crossed multiplied and ...
- Math - Could someone please explain this problem to me? I will show you what I ...
- Math Pre-Algebra - Simplify the Expression(-8/15)+(1/15). Show how to simplify ...
- Algebra - Can you please check my work? You have helped other students I know. ...

More Related Questions