Answer:
a) l = 5 + 2w
b) P = 2(l +w) = 2(5 +2w +w)
c) w = 8 cm, l = 21 cm
Explanation:
a) Using w for width, twice the width is 2w, and 5 more than that is 5+2w. This is your expression for l:
... l = 5 + 2w
b) The perimeter is the sum of the lengths of all sides, so is the sum of twice the length and twice the width.
... P = 2(l +w) = 2(5 +2w + w) . . . . substituting for l using the expression of (a)
c) Substituting the given perimeter, we have ...
... 58 = 2(5 +3w) = 10 + 6w . . . . . collect terms, eliminate parentheses
... 48 = 6w . . . . . . . . . . . . . . . . . . subtract 10
... 8 = w . . . . . . . . divide by 6
... l = 5 + 2·8 = 21 . . . . . find length using the formula for it
Dimensions are in centimeters, so we can write the solution as ...
- width = 8 cm
- length = 21 cm
