Answer to Question #187064 in Geometry for john

Question

A teacher's 2 inch by 5 inch cell phone screen is projected on a wall

with a scale factor of 1:25 to demonstrate a new teaching app. What is the area

of the projected image in square inches?

Answer 1

• Measurements of teacher’s cell phone is  2 inches  by 5 inches   
• We are given the scale factor 1:25

This implies that 1 inch   on teacher’s cell phone represents 25 inches on the projected image

• The length of the projected image

1 inch  on teacher’s cell phone represents 25 inches   on the projected image

Therefore 5 inches    on teacher’s cell phone represents (5 × 25) inches   on the projected image

Therefore The length of projected image is (5 × 25) inches = 125 inches   

• The width of the projected image

1 inch   on teacher’s cell phone represents 25 inches on the projected image

This implies that 2 inches    on teacher’s cell phone represents (2 × 25) inches on the projected image

Therefore the width of projected image is (2 × 25) inches = 50 inches

• Area of the projected image   

Area = length × width 

     = 125 × 25

     = 6,250 square inches