which math fraction is greater through approximation:
10/21 or 15/28?
One way to answer would be to convert to common denominators.
10/21 = 40/84
15/28 = 45/84
so 15/28 is quite a bit larger.
Here is another way:
10/21 is 0.5/21 or 1/42 larger than 1/2
15/28 is 1/28 larger than 1/2.
Since 1/28 > 1/42, 15/28 is larger
here is yet another "very old-fashioned" way:
write the fractions side by side, and take the product of the "diagonals"
10/21 vs 15/28
diagonal leaning left = 10x28 = 280
diagonal leaning right = 21x15 = 315
since 280 < 315
10/21 < 15/28
My second method contained an error but got the right answer.
10/21 is 1/42 LESS than 1/2, not greater.
15/28 is greater than 1/2.
I should have seen that right away.
nice!
(probably better than some of the "methods" used these days to teach fractions)
Cool game !
OH,MY Goodness
went to home page
http://www.echalk.co.uk/
The Blob Game is hilarious.
Catch what happens to the blob when you pick the wrong one.
15/56 8/35
To determine which fraction is greater through approximation, we can convert both fractions to decimals and then compare them.
To convert a fraction to a decimal, divide the numerator (the top number) by the denominator (the bottom number).
For the fraction 10/21:
10 ÷ 21 = 0.47619 (rounded to five decimal places)
For the fraction 15/28:
15 ÷ 28 = 0.53571 (rounded to five decimal places)
Comparing the two decimals, we see that 0.53571 is greater than 0.47619. Therefore, the fraction 15/28 is greater than the fraction 10/21 through approximation.
increase the first by a factor of 28/21 or 4/3 or 1.3
10/21 * 1.3/1.3= 13/28
Which means 15/28 is the larger.
http://www.echalk.co.uk/tasters/taster2/taster.html
A nice Texas estimating fractions exercise (Texas=UK)