do this is less then 40sec QR

[future_dentist]

---

Members do not see this ad.

Can anyone do the following quickly:

(7/12) + (2/9) - (5/6)

Ans= -1/36

can anyone give me step by step instruction:

this is how i did it:

=((63+24)/108) -(5/6)

=(522-540)/(648)

= -18/648= -1/36

 

[tinman831]

Can anyone do the following quickly:

(7/12) + (2/9) - (5/6)

Ans= -1/36

can anyone give me step by step instruction:

this is how i did it:

=((63+24)/108) -(5/6)

=(522-540)/(648)

= -18/648= -1/36

You can do it in about 20 seconds. First convert -5/6 into -10/12 and add to 7/12 to get -3/12. Then find a common denominator for -3/12 and 2/9 which is 36. Then add them both together.

 

[egots]

(21/36) + (8/36) - (30/36)

 

[vha7777]

It looks like you went a really around about way to find the answer to this question. The least common denominator for all three fractions is 36 so you get

(7/12)(3/3) + (2/9)(4/4) - (5/6)(6/6)

21/36 + 8/36 - 30/36 = -1/36


To do questions like this fast there is almost always a least common denominator for all of the fractions. Usually it will depend on the largest number (12 in this case) and just figure out it's multiples and if the other numbers will divide into it easily.

 

[Fariba]

Yeah!! I can ACTUALLY help you with this... even though I suck at math! The best way to do these problems is look for the LCD. In this case, putting 36 for the denominator on all of them. Then you would have to

multiply 7x3 (12 times 3 = 36),
multiply 2x4 (9 times 4 = 36),
multiply 5x6 (6 times 6 =36).

So now, you have the equation 21 + 8 - 30 (all over 36) ....

sooooo, 21 + 8 = 29. 29 - 30 = -1 .... and dont forget that you still have the 36 in the denominator.

Make sense?

 

[Fariba]

It looks like you went a really around about way to find the answer to this question. The least common denominator for all three fractions is 36 so you get

(7/12)(3/3) + (2/9)(4/4) - (5/6)(6/6)

21/36 + 8/36 - 30/36 = -1/36


To do questions like this fast there is almost always a least common denominator for all of the fractions. Usually it will depend on the largest number (12 in this case) and just figure out it's multiples and if the other numbers will divide into it easily.

Aw man, you beat me to it. I was so excited to help someone with a math question and you just HAD to go and steal my thunder. Thanks a lot!
hahaha, just kidding

 

[joonkimdds]

Can anyone do the following quickly:

(7/12) + (2/9) - (5/6)

Ans= -1/36

can anyone give me step by step instruction:

this is how i did it:

=((63+24)/108) -(5/6)

=(522-540)/(648)

= -18/648= -1/36

I can use my TI-83 Plus calculator and solve it in 5 sec

 

[tinman831]

I can use my TI-83 Plus calculator and solve it in 5 sec

copy and paste into google search bar = 1 sec 😛