Homework Help: 3rd grade Math

Posted by Dominique on Thursday, January 6, 2011 at 12:25am.

In Harry's attic there are 3 spider webs. The first web is twice as large as the second. The 3rd web is 3 inches larger than the 1st web. The combined width of the 3 webs is 1 foot and 6 inches. How long is each web?

Please provide explanation along with answer. Thank you in advance.

3rd grade Math - PsyDAG, Thursday, January 6, 2011 at 12:12pm
The original data is given in terms of area, but the width is not in the same units.

If area 1 = x, then area 2 = 2x and area 3 = x + 3.

If the total area = 18 square inches, then

x + 2x + x + 2 = 18

Then you can solve for x.

4x + 2 = 18

4x = 16

x = 4
3rd grade Math - helper, Thursday, January 6, 2011 at 12:18pm
I'll answer since this is unanswered, but, I don't think this is how a third grade student is expected to do this problem.

w = width of web
w = size in inches of the 2nd web
2w = size in inches of the 1st web
2w + 3 = size in inches of the 3rd web

1'6" = 18 inches
w + 2w + (2w + 3 ) = 18
5w + 3 = 18
5w = 15
w = 3

1st web = 3 inches
2nd web = 6 inches
3rd web = 9 inches
Total combined width = 18 inches
3rd grade Math - Reiny, Thursday, January 6, 2011 at 12:46pm
I would be very interested to learn how a grade 3 teacher would handle this type of question without relying on algebraic methods such as shown above by
PsyDAG and helper.

This sure looks like some fancy advanced grade 3 stuff.
3rd grade Math - Elizabeth, Monday, January 10, 2011 at 5:32pm
what is symmetry
3rd grade Math - Anonymous, Tuesday, June 12, 2012 at 3:55pm
whats up

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