Question

Estimate the sum of 12.43, 17.47, 18.63 and 6.39 by each of the following methods:
(a) Rounding off the numbers to the nearest integers
(b) Using the compensation strategy.

Answer 1

For (a), I did it in this way
Sum = 12 + 17 + 19 + 6 = 54
What about (b), how should I do it?

Answer 2

in a, what happened to the the 47?

Answer 3

Sorry.. typo. 17.47

Answer 4

12 + 17 + 19 + 6
= (12-2) + (17+3) + (19+1) + (6-2) ???
tell you the truth, i've never heard of the compensation strategy...:(

Answer 5

Nope :(
I don't like estimation!!!!

Answer 6

The answer of (b) is different from (a), according to the book.

Answer 7

sorry.... idk how to do it... i'm not familiar with the compensation thingy...

Answer 8

It's okay. Thanks for trying!!!

Answer 9

for b i think its something like this
10+ 20 + 20+ 5 -1 =54

Answer 10

i think thats how it is, you round the numbers to the closest five or tens then, you add up what you subtracted/added from each to the end

Answer 11

Nope. It's not 54...

Answer 12

a) 12 + 18 +19 +6
b) 10 + 20 +20 +5 =55?

Answer 13

For (a), I think it's 12 + 17 + 19 + 6 =54
For (b), you've got the answer, but why did you do in that way?

Answer 14

b says use the compensation strategy

Answer 15

Yes?!

Answer 16

But that compensation strategy exactly is?

Answer 17

*that -> what

Answer 18

this is where i got it
http://wiki.answers.com/Q/How_do_you_do_math_compensation_subtraction

Answer 19

i'm not sure if that is exactly what your book asks for

Answer 20

But you're getting the exact answer. In this case, it's not.

Answer 21

Another interesting thing is that, why does it compensate the last one, but not the first one - i mean both of them together.

Answer 22

here's another good explanation, scroll to the 6th page
http://www.coolclass.ca/pdf/Estimation.pdf

Answer 23

I'm not sure what you mean

Answer 24

Hmm... like the questions there are all integers, not decimal number.
When we round the number
12.43, 17.47, 18.63 and 6.39
12 17 19 6
Compensate:
10 (+2) 20 (-3) 20 (-1) 5(+1)
=> 10 + 20 + 20 + 5
=> 55 ....
like that?

Answer 25

looks about right

Answer 26

well i hoped that helped

Answer 27

But why would 17 change to 20?
At first, I rounded it to 15... but i can't get the answer. So, I changed it to 20

Answer 28

its why I used 18 instead of 17. Instead of rounding 17.47 directly up to 17, I rounded it up to 17.5, and then rounded up to 18.
Then i borrowed numbers already in the problem.
12 loses to and gives it to 18, which makes it 10 + 20
while 6 loses one and gives it to 19, which makes it 20 + 5.
all together its 10+20+20+5

Answer 29

Oh... I see your point!!! Thanks a ton!!!!

Answer 30

no prob :)