Help with a fractions question please!
Moderators: Section Moderators, Forum Moderators
Help with a fractions question please!
Can someone help me explain how to do this question which was on a practice test my son was given?
If 1/a + 1/b = 7/10
What are the values of "a" and "b"?
Personally I haven't a clue, so any help much appreciated!
If 1/a + 1/b = 7/10
What are the values of "a" and "b"?
Personally I haven't a clue, so any help much appreciated!
1/a + 1/b = 7/10
1*b + 1*a ...........7
_________ = _____
a*b ....................... 10
a+b .................. ..................... 7
_____ ...................= ................. ______
a * b ........................................ 10
These being equivalent fractions
a+b = 7 and a*b = 10
If you now find factors of 10 such that they add upto 7, which is the answer
a, b will be 5,2
1*b + 1*a ...........7
_________ = _____
a*b ....................... 10
a+b .................. ..................... 7
_____ ...................= ................. ______
a * b ........................................ 10
These being equivalent fractions
a+b = 7 and a*b = 10
If you now find factors of 10 such that they add upto 7, which is the answer
a, b will be 5,2
-
- Posts: 1245
- Joined: Fri Jul 06, 2007 9:31 pm
or by observing split into two terms...
7/10
is...
6/10 + 1/10 which is... 3/5 + 1/10... i.e. not of the form 1/a+1/b so ignore...
5/10 + 2/10 which is... 1/2 + 1/5... Looks Good
4/10 + 3/10 which is... 2/5 + 3/10... i.e. not of the form 1/a+1/b so ignore...
3/10 + 4/10 ... hang on... we've done this one so STOP.
7/10
is...
6/10 + 1/10 which is... 3/5 + 1/10... i.e. not of the form 1/a+1/b so ignore...
5/10 + 2/10 which is... 1/2 + 1/5... Looks Good
4/10 + 3/10 which is... 2/5 + 3/10... i.e. not of the form 1/a+1/b so ignore...
3/10 + 4/10 ... hang on... we've done this one so STOP.
Animis opibusque parati
Oh boy, don't think I will be able to explain it very easily with confusing my son! I guess the split terms method would be the easiest way to go, as he should at least know that the denominator has to be the same when adding fractions.
Do these types of questions come up very often in 11+ exams or can I just ignore it and hope for the best? (she asks, with fingers crossed)
Do these types of questions come up very often in 11+ exams or can I just ignore it and hope for the best? (she asks, with fingers crossed)