Estimating sums and differences?

Question

Can someone just help me a little with my homework? I'm not nessescarily asking for the answers, but can you just explain how you do it?

For example heres the questions they are asking for. I just dont understand. An easy explainer would be great for me!

1. 3/5 + 7/9

2. 10/13 + 3/7

5. 2 and 4/5 - 1 and 5/6

6. 1 and 6/10 + 1 and 3/7

8. 4 and 4/5 - 3 and 2/9

9. 15/18 + 1 and 3/7

10. 2 and 2/11 + 1 and 5/9

12. 13/16 + 5/6

And i am NOT asking for answers because i do not cheat. I am just showing u some of the examples so you can help me understand better if you can. Please help i dont wanna be mean im just asking for some explaining. And if you can plz show me how you got the answer. Thank you everyone who tried their best! Thaaaaanks a bunch it would be such a big help i cannot thank you enough if you help. Thanks everyone!

Answer 1

you always need to find a common denominator. Take example the first one, the lowest common denominator is 45.

3/5 =27/45 because you take 5X9 which equals 45, so then you take 9x3 which equals 27 on the top

for the bottom 7/9=35/45 9X5 equals 45. So what is 5 X7 thats 35.

so then take 27/45 + 35/45 which equals 62 over 45. and since your numerator is larger the the denominator it makes it an impromper fraction. So the next step would be to divide 62 by 45 which equals 1 and remainder of 17. Which is written 1 and 17/45 unless you can reduce it down further...

hope i helped a little bit! =)

Answer 2

THIS IS ESTIMATING
NOT
SOLVING

"See" the picture. Mental Math.

Think about what part of the whole each is.

1) 3/5 - 5 parts in a whole Half would be 2.5 parts.
Equals - 6/10, Little over a half
Three fourths is 7.5/10 Less then 3/4

7/9 - 9 parts in a whole Half would be 3.5 parts
Two thirds would be 6/9

Estimate: 1/2 plus 2/3 = 1 1/3


8) 4/5 - Think almost all the 5 parts
2/9 - Think less then 1/3 of the 9 parts

Hope this helps a little.

Answer 3

Hi Kayla. If I understand your question correctly, the challenge is NOT to find the exact answer, but rather, to ESTIMATE the answer (quickly get close to the right answer) .

1) 3/5 + 7/9

7/9 is 'close' to 7/10 and 3/5 is the same as 6/10. So a close 'estimate' of their sums is 7/10 + 6/10 ~ 13/10

2) 10/13 + 3/7

Do this the same way. 10/13 is close to 10/14 and 3/7 is the same as 6/14. So an estimate of their sums is 10/14 + 6/14 ~ 20/14.

Hope this helps you. Best wishes and good luck. (Note: ~ means 'about equal to')

Answer 4

to add and subtract these numbers the number on the bottom must be the same. i usually multiply the fractions by the number under the other one ex #1 3/5 i would multiply by 9 making it 27/45 and 7/9 i would multiply by 5 making it 35/45 then add the tops 27+35= 62 then put it over the 45 62/45 and reduce it 1 17/45