which fraction is bigger?

[spudqueen]

Which is the biggest fraction out of 2/5 and 3/7? And how do you work it out?

[newquizzer]

To compare you need to find a number that is divisible by 5 and 7 and recalculate the fractions.

In this case 35 can be used. 2/5 is 14/35 and 3/7 is 15/35. Now you can see which is bigger

[Big Al1st]

5 divided by 2 times 100 = 40%

7 divided by 3 times 100 = 42.9%

Therefore 3/7 is slightly bigger

I reckon ( I hope)

[parkesquay]

Firstly find the lowest common denominator (LCD). In this case it is 35 i.e. this is the lowest number that both 5 & 7 will divide into. Then divide each root ( 5 & 7) into the LCD.

So in 2/5 case the 5 divides into 35 - seven times. Then mutiply the 2 x 7=14.

In the 3/7 case the 7 divides into 35 - five times. Then multiply the 3 x 5= 15.

Ergo 2/5 = 14/35 and 3/7 = 15/35. Therefore 3/7 is the bigger fraction.

[spudqueen]

Wow, what quick answers!! Yes, it all vaguely rings a bell (it's a long time since I was at school!). Thank you all for your help.

[fo3nix]

Convert the fractions to decimal, which is easier to look and and spot the biggest instantly.

The "/" between them means divide. So divide them:

2/5 = 0.4
3/7 = 0.43...

Hence 3/7 is slightly larger.

(of course, this is relying you have a calculator at hand)

[Jay70]

You dont really need to find the LCD in this case just a common denominator as the numbers are small. To do this just multiply the denominators. Then multiply the numerator of one fraction with the demoninator of the other for each fraction and put each over your CD then the rest is self evident.

5 x 7 = 35

7 x 2 = 14

5 x 3 = 15

therfore 2/5 = 14/35

and 3/7 = 15/35

so 3/7 is larger by 1/35

[spudqueen]

THAT'S they way I did it in school, thanks for that reminder Jay70.

[Gef]

fo3nix gives the sensible answer. If you don't have a calculator (most computers have a built in one) then use long division or do it in your head.

Big Al's answer is I'm afraid wrong.

5 divided by 2 times 100 is 250% not 40%.

[mibn2cweus]

Convert one to the others denomination for comparison.
Examples . . .
(2 / 5) X 7 = 2.8/7 (< 3/7)
or
(3 / 7) X 5 = 2.14/5 (> 2/5).

[Jay70]

Gef - giving the answer as anything else other than a fraction i.e. decimal or percentage is only sensible if you've been asked to do so.

[Gef]

Jay, have you read my answer carefully enough?