I can't figure out this problem! Do I multiply or add? Same for the 2nd one!

1. Robin has read 3/4 of a book. Mark said he had read 1/2 as much as robin. What fraction of the book has mark read? (I have 2 show my work)

2. a bycicle is on sale for 2/3 of its original price . If the original price is $354, what is the sale price?

I don't need the answers but the strategies to answer them.

In both cases you need to multiply.

1/2 times 3/4 will give you the fration of the book Mark has read, and 2/3 times 354/1 will give you the sale price.

Does that help?

In both cases you need to multiply.

1/2 times 3/4 will give you the fration of the book Mark has read, and 2/3 times 354/1 will give you the sale price.

Does that help?

Sorry, posted twice by accident.

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Originally Posted by YoungHyperLink

In both cases you need to multiply.

1/2 times 3/4 will give you the fration of the book Mark has read, and 2/3 times 354/1 will give you the sale price.

Does that help?

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Yes thanks so much! You saved my math grade!:):D

My pleasure. As long as you are not looking for answers to your homework problems, but just for help in understanding them, remember there are lots of people willing to help here.

Q 1) 3/4 X 1/2 = (?)
Q 2) Original Price $354 X 1/3 = (X) $354 - X = Sales price.

Except that two of you just gave out the answers without a bit of the strategy.

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Originally Posted by morgaine300

Except that two of you just gave out the answers without a bit of the strategy.

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Hmm... not the answers, exactly, but I see what you mean. I´ll try to explain the concept next time and not the procedure, if that's what you mean. Thanks.

There is another way of doing #2. I might confuse you. I might not.

2. a bicycle is on sale for 2/3 of its original price . If the original price is $354, what is the sale price?

On first glance it almost looks like a percentage problem.

X% of $354 is Y

That's solved by X/100 = Y/$354

Percents can be written as decimals, so instead of X/100 the equation is

2/3 of $354 is Y

When you see it that way, 2/3*$354 is the answer

or even

2/3 = Y/354 --> 2/3 * 254

also 2/3 is 2/3*100 or 66.666666... %

or 66.6666% of 254

and for #1, by inspection. 50% of 3/4
or book is 100% or 1

R read 3/4*100% or 75%
M = 1/2 * R or M = 50% of R

or M =50% of 75%

M = 1/2 * 3/4 because 50% = 1/2 and 75% = 75/100 or 3/4

Or at least the concept along with the procedure. Since the question was whether to multiply or add, saying to multiply isn't really explaining the why. (Pictures are good, but that's such a pain in the rear on here.)

Quote:

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Originally Posted by morgaine300

Or at least the concept along with the procedure. Since the question was whether to multiply or add, saying to multiply isn't really explaining the why. (Pictures are good, but that's such a pain in the rear on here.)

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Yeah, my math teachers always said start with a picture if at all possible. And we aren't supposed to do the homework here and supply the answers.

Strange, none of my math teachers said to start with pictures. I had to figure that one out for myself. Fortunately I did, or I would've spent the rest of my life thinking I was stupid at math.

Pictures are worth 1000 words... or so it is said. I use pictures when I got stuck, it's the best way to get out. If that does not help, then, I remain stuck :o

- Why multiply?
You read the problem as "'half' of 'three quarters'". That means, you need to find 3/4 divided by two. That is the equivalent of 3/4 * 1/2, since multiplying by half is the same as dividing by two.

- Second number.
Perhaps using proportions will help?

1 (whole) -> $354
2 -> 354 * 2
1/2 -> 354 * 1/2
Etc

So, 2/3 -> 354 * 2/3