# can you help with this maths question for my 9 year old?  The answer section says D but I would like to help him understand why.  Thanks.?

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• 1 month ago

When dealing with mathematics, one of the tricks is to ensure that the numbers represent the same thing, like apples, SO one apple + one apples = 2 apples or one orange + one orange = two oranges, but one apple + one orange is NOT two apples or two oranges.

To be able to add them together, we have tofind a way of making the apples and oranges the same --- call then fruit:

so one fruit + one fruit = two fruit

In this problem we are dealing with fractions, In fractions, the denominators (the number under the short line) are like apples and oranges

1/12 is NOT the same as 1/36

How can we make these comparable?

well, 36 = 3 * 12

hence 1/2 = 3/36

so is 5/12 less than 16/36?

that's like comparing 5 lots of 3/36  which is the same as 15 lots of 1/36 to 16 lots of 1/36

or asking " is 15/36 less than 16/36?" (yes, 15 is less than 16).

do the same with the others.

3/7 = 15/35  vs 16/35 (yes, 15 is less than 16).

7/13 = 21/39 vs 22/39 (yes, 21 is less than 22).

10/11 = 30/33 vs 29/33 (no, 30 is greater than 29.

)hope this helps....

• 1 month ago

The answer is D.  10/11 is equal to 30/33, which is 1/33 greater than 29/33, not less.

To compare two fractions, the denominators have to be the same.Any number divided by itself equals 1,  so to make the denominators in the two fractions in D the same, you have to multiply 10/11 by 3/3, which will give you 30/33,which has the same denominator, 33, as the other fraction, 29/33. Now you can see that 30/33 is 1/33 greater than 29/33.  Since < means "less than", the expression in D is false.

• 1 month ago

10/11 = 30/33 which is GREATER than 29/33

• 1 month ago

Let's take the first inequality as an example:

5/12 < 16/36.

Now cross multiply the left numerator times the right denominator 5*36 = 180 keep this on the left side and the left denominator and the right numerator  12*16=192 keep this on the right side.

Now compare 180 from the left answer is less than 192 from the right. So the first one is true.

Do this for each inequality to see which one is false.

I hope this helps!

Cipherman

• 1 month ago

the answer is D because 10/11 is the same thing as 30/33 and the other fraction is 29/33. Now that we have fractions with the same denominator. Now all we need to do is look at the numerators and compare. So 30 is actually greater than 29.

• RockIt
Lv 7
1 month ago

Because in A. B. and C. when we multiply the left hand of the inequality by,  actually, by 3/3=1 we maintain the left hands value because p/q*1=p/q, q<>0.

But, in D, we multiply 10/11 * 3/3 = 30/33 which is not < 29/33 because 30>29.

• 1 month ago

others have explained the solution.

i shall show you the tricks to decide quickly

5/12 < 16/36

cross multiply

5*12 ; 12*16

60 ; 192 you know that 60<192

similarly

10/11 ; 29/33

10*33 ; 29*11

330 ; 319

so 330 > 319 so, what is indicated is false

• JOHN
Lv 7
1 month ago

5/12 < 16/36 is the same as 5 x 36 < 12 x 16, which is the same as 180 < 192. True.

3/7 < 16/35 is the same as 3 x 35 < 7 x 16, which is the same as 105 < 112. True.

7/13 < 22/39 is the same as 7 x 39 < 13 x 39, which is the same as 273 < 507. True.

10/11 < 29/33 is the same as 10 x 33 < 11 x 29, which is the same as 330 < 319. False.

• 1 month ago

First of all, make the fraction equal :

A. 5/12 = 15/36

B. 3/7 = 15/35

C. 7/13 = 21/39

D. 10/11 = 30/33

Now compare the top numbers & you will see answer D. 30 is lesser than 29 which is wrong.

• Vaman
Lv 7
1 month ago

What you can do is write it as 10/11 < 29/33. Show him that  2/3 < 3/4 by this logic. Multiply both sides by 3, You will have 2 <9/4. Now again multiply by 4. You will get 8<9/ True.. Multiply by 11

10 < 29*11/33= 10 < 29/3. Multiply by 3. You get 30 <29. This is not true. You take 12 marbles. Make 3 parts and take 2 parts and count.You get 8.  Again make 4 parts and take 3 parts and count. You get 9 now.