Wednesday

March 4, 2015

March 4, 2015

Posted by **Paul** on Wednesday, December 1, 2010 at 6:52pm.

- Math-3rd grade -
**bobpursley**, Wednesday, December 1, 2010 at 7:53pmSo you want the sum of 1+2+3+....+12+13+14.

Well, there are 14 numbers. Divide them in half at 7, divide them again at 3 1/2 and 10 1/2

so 1/4 of the numbers are closest to zero, 1/2 of the numbers are closest to 7, and 1/4 of the numbers are closest to 14

Sum= 1/4*14*1+1/2*14*7+ 1/4*14*14

= 3.5+49+49=102 about

This is not 3rd grade, I had this method in highschool.

Now here is another method, a college method, call the sum of arithemetic series..

Sum= 14/2 *(1+14)=7*15=105

So the estimate was not far off.

- Math-3rd grade -
**imani**, Thursday, August 25, 2011 at 8:41pmform

**Answer this Question**

**Related Questions**

3rd grade - Use compatible numbers to complete this problem. Then estimate the ...

3rd grade math - front end estimation to estimate the sum...like..436+517...

math - 4th grade math homework. rounding sums and differences. paper say "round ...

6th Grade Math - How do I know whether to round all the numbers first, THEN ...

3rd grade - if i have a hundred chart to find all the 2 digit numbers in which ...

3rd grade math - i need help!! if the estimate is greater than or equal or 1,500...

math - consider the sum 3/5+3/4. round each fraction and estimate the sum. add ...

3rd math - April needs to estimate the sum of 427 and 338 should she round to ...

3rd grade math - Sven is thinking of two numbers. The sum is 12. The difference ...

3rd grade math - which of these numbers do not round to 400.347, 369, 413, 448