Question

A photo frame of 24 cm long and 16 cm wide is edged with a piece of wood of 2cm width. Find the cost of edging at the rate of rupee 7 per square cm.

Answer 1

aloha!

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we know that area of picture would be length × breadth
                                                              = 24 × 16
                                                              = 384

now the total area combining the photo and frame would be having 

length    = 24 + 4 { as width is added to both sides }
              = 28
breadth = 16 + 4
              =  20 

now total area = 28 × 20
                         = 560 cm²

the area of frame would be 560 - 384 
                                            = 176 cm²

now the rate of edging is given to be 7rs per cm².
so,

=176 × 7
= 1232 rs

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hope this helps you :)