Grades 5-6 Video Solutions 2021-video 2021 5-6/15

Video Transcription

15. Three rectangles of the same height are positioned as shown. The numbers within the rectangles indicate their areas in cm2. If AB equals 6 cm, how long is CD?  The area bounded by AB and this height of this general bigger rectangle has an area of 12 plus 18 equals 30. We know that the area of a rectangle is area equals height  times width, so 30 equals height times 6, and the height must be 5 cm. Next, the area bounded by CD and the height has an area of 18 plus 22 equals 40. The area again is height  times width, this time we know the height, so 40 equals 5 times this width. Width is therefore 8 cm. So we can say that CD, which is the width, is 8 cm, the answer must be C.

Video Summary

15. Three rectangles of the same height are positioned as shown. The numbers within the rectangles indicate their areas in cm2. If AB equals 6 cm, how long is CD? The area bounded by AB and this height of this general bigger rectangle has an area of 12 plus 18 equals 30. We know that the area of a rectangle is area equals height times width, so 30 equals height times 6, and the height must be 5 cm. Next, the area bounded by CD and the height has an area of 18 plus 22 equals 40. The area again is height times width, this time we know the height, so 40 equals 5 times this width. Width is therefore 8 cm. So we can say that CD, which is the width, is 8 cm, the answer must be C.

Keywords

rectangles

areas

height

width

calculation