Question

name date complete each multiplication equation to find the area of each rectangle. 1. 40 cm 8 cm a = l×w a = _×_ a = _ the area is _ sq cm. 2. 30 m 9 m a = l×w a = _×_ a = _ the area is _ sq m. write an equation to find each unknown side - length. then fill in the blanks. 3. the area is 90 sq cm. d cm 9 cm equation: _ d = _ the unknown side - length is _ cm. 4. the area is 420 sq m. 7 m b m equation: _ b = _ the unknown side - length is _ m.

Explanation:

Step1: Find area of first rectangle

Use formula $A = l\times w$, where $l = 40$ cm and $w = 8$ cm. So $A=40\times8 = 320$.

Step2: Find area of second rectangle

Use formula $A = l\times w$, where $l = 30$ m and $w = 9$ m. So $A = 30\times9=270$.

Step3: Find unknown side of third rectangle

Given $A = 90$ sq cm and $w = 9$ cm. Use formula $A=l\times w$, then $l=\frac{A}{w}$. The equation is $90 = d\times9$, so $d=\frac{90}{9}=10$.

Step4: Find unknown side of fourth rectangle

Given $A = 420$ sq m and $w = 7$ m. Use formula $A=l\times w$, the equation is $420=7\times b$. Then $b=\frac{420}{7}=60$.

Answer:

1. $A = 40\times8=320$, the area is 320 sq cm.
2. $A = 30\times9 = 270$, the area is 270 sq m.
3. Equation: $90=d\times9$, $d = 10$, the unknown side length is 10 cm.
4. Equation: $420 = 7\times b$, $b = 60$, the unknown side length is 60 m.