Help needed with Fraction questions

Hi all,

I was looking for a maths homework help site and came across here, (Smile) hoping I can find some help here.

My questions are of pretty basic level but a bit tricky involving fractions.

**Q1) Colin buys a bag of flour. He uses 1/3 to bake a cake and 1/2 to make a loaf. **

What fraction of the bag of flour is left?

Q2) Lee and Mary have a packet of same sweets. Mary eats 1/3 of her packet. Lee eats 3/4 of his packet. Find the diffrence between the fraction Mary eats and the fraction Lee eats ? I subtracted the fractions and got 5/12 which I checked is correct.

**Lee gives his remaining sweets to Mary. What fraction of a packet does Mary now have? **

Q3) Jon, Billy and Cathy are the only candidates in a election. Jon got 7/20 of the votes. Billy got 2/5 of the votes.

What fraction of the votes did Cathy get?

Which candidate won the election?

Q4) A school has pupils in years 7 to 13.

7/12 of its pupils are in years 7 to 9 and 3/10 of its pupils are in years 10 and 11.

What fraction of the pupils in the school are in years 12 and 13?

Q5) A bag of sweets contains chocolates, toffees and mints.

2/5 are chocolates and there are an equal number of toffees and mints.

What fraction of the sweets are toffees ?

I also have some more word questions that I am stuck with. Can someone please help me solve these ?

Re: Help needed with Fraction questions

Q1) Colin begins with a whole bag of flour, then subtract 1/3 of it for the cake and 1/2 of it for the loaf. So he is left with:

$\displaystyle 1-\frac{1}{3}-\frac{1}{2}$

What is the lowest common denominator?

Q2) You were able to correctly calculate:

$\displaystyle \frac{3}{4}-\frac{1}{3}=\frac{9}{12}-\frac{4}{12}=\frac{5}{12}$

So, I assume you know how to add and subtract fractions with different denominators.

For the second part of this question, we need to find what portion remains for Lee and Mary.

Mary ate 1/3 of her packet, leaving her with $\displaystyle 1-\frac{1}{3}$.

Lee ate 3/4 of his packet, leaving him with $\displaystyle 1-\frac{3}{4}$.

If Lee gives his remnant to Mary, we find what portion of a packet she has by adding the two remnants. Can you finish?

Q3) Let C represent the fraction of the votes Cathy got. We then require:

$\displaystyle C+\frac{7}{20}+\frac{2}{5}=1$

$\displaystyle C=1-\frac{7}{20}-\frac{2}{5}$

Once you find C, you may compare the 3 fractions directly by writing them with the same denominator.

Q4) Let F represent the fraction of the students in years 12 and 13. We then require:

$\displaystyle F+\frac{7}{12}+\frac{3}{10}=1$

$\displaystyle F=1-\frac{7}{12}-\frac{3}{10}$

Q5) Let T represent the fraction of toffees, and since there is the same fraction of mints as toffees, we may state:

$\displaystyle T+T+\frac{2}{5}=1$

$\displaystyle 2T=1-\frac{2}{5}$

Now solve for T.

Give these problems a try now, and if you get stuck, we will be glad to assist.

Re: Help needed with Fraction questions

Hi again thanks for answering.

Q1) it is 1/6 6 being the lowest common denominator right ?

Q2) Yes once i know what i have to do whether its subtract or add then its fine, its just that I dont know when .

You said we add the remainders to get the answer, remainders are 1/3 and 3/4 so if i add them together i get 1/12 ?

Q3) I am not sure where the one comes from ?

We find C by subtracting the two fractions 7/20 - 2/5 and I get 1/20 for C ? is that correct ?

Q4) Same problem as I dont know where the 1 comes from, and are we subtracting the two fractions 7/12 - 3/10 ?

Q5) Same thing with this question too. I dont get how we get 1 from ?

Re: Help needed with Fraction questions

Quote:

Originally Posted by

**MissR** Hi again thanks for answering.

Q1) it is 1/6 6 being the lowest common denominator right ?

Yes. $\displaystyle 1-\frac{1}{3}-\frac{1}{2}=\frac{6}{6}-\frac{2}{6}-\frac{3}{6}=\frac{6-2-3}{6}=\frac{1}{6}$

Quote:

Originally Posted by

**MissR** Q2) Yes once i know what i have to do whether its subtract or add then its fine, its just that I don't know when .

You said we add the remainders to get the answer, remainders are 1/3 and 3/4 so if i add them together i get 1/12 ?

No, the remnants are:

$\displaystyle 1-\frac{1}{3}=\frac{2}{3}$

$\displaystyle 1-\frac{3}{4}=\frac{1}{4}$

So, Mary will have:

$\displaystyle \frac{2}{3}+\frac{1}{4}$

I will let you complete the addition.

Quote:

Originally Posted by

**MissR** Q3) I am not sure where the one comes from ?

We find C by subtracting the two fractions 7/20 - 2/5 and I get 1/20 for C ? is that correct ?

The 1 comes from the fact that all of something is the whole thing, which we represent by a 1.

No, we find C from:

$\displaystyle 1-\frac{7}{20}-\frac{2}{5}=\frac{20}{20}-\frac{7}{20}-\frac{8}{20}$

Complete the operations, then reduce.

Quote:

Originally Posted by

**MissR** Q4) Same problem as I dont know where the 1 comes from, and are we subtracting the two fractions 7/12 - 3/10 ?

We know the 3 fractions, when added together represent all of the students, which is 100% of them or 1.

No, we want to compute:

$\displaystyle 1-\frac{7}{12}-\frac{3}{10}=\frac{60}{60}-\frac{35}{60}-\frac{18}{60}$

Quote:

Originally Posted by

**MissR** Q5) Same thing with this question too. I don't get how we get 1 from ?

The fractions of toffees, mints and chocolates make up the whole bag, so we add their fractions to get 1.