CBSE Class 8 Answered

A hall is 36m long and 24m broad. Allowing 40 square meters for doors and windows, the cost of papering the wall at Rs 8.40 per square meters is Rs 4704. Find the height of the hall.

Asked by disha2.bhardwaj | 13 Jan, 2015, 10:14: AM

Expert Answer

G i v e n space t h a t space l equals 36 space m space a n d space b equals 24 space m L e t space apostrophe h apostrophe space b e space t h e space h e i g h t space o f space t h e space w a l l. A r e a space o f space f o u r space w a l l s equals 2 l h plus 2 b h A r e a space o f space d o o r s space a n d space w i n d o w s equals 40 space m squared T h u s comma space t h e space a r e a space o f space f o u r space w a l l s space equals 2 l h plus 2 b h minus 40 C o s t space o f space p a p e r i n g space t h e space w a l l space p e r space s q u a r e space m e t r e equals R s.8.40 T o t a l space cos t space o f space p a p e r i n g space t h e space w a l l equals R s.4704 rightwards double arrow T o t a l space a r e a space e x c l u d i n g space t h e space a r e a space o f space d o o r s space a n d space w i n d o w s cross times C o s t space o f space p a p e r i n g space t h e space w a l l space p e r space s q u a r e space m e t r e equals T o t a l space cos t rightwards double arrow open parentheses 2 l h plus 2 b h minus 40 close parentheses cross times 8.40 equals 4704 rightwards double arrow open parentheses 2 cross times 36 h plus 2 cross times 24 h minus 40 close parentheses cross times 8.40 equals 4704 rightwards double arrow open parentheses 2 cross times 36 h plus 2 cross times 24 h minus 40 close parentheses equals fraction numerator 4704 over denominator 8.40 end fraction rightwards double arrow 2 cross times 36 h plus 2 cross times 24 h minus 40 equals 560 rightwards double arrow 2 cross times 36 h plus 2 cross times 24 h equals 560 plus 40 rightwards double arrow 2 cross times 36 h plus 2 cross times 24 h equals 600 rightwards double arrow open square brackets 2 cross times 36 plus 2 cross times 24 close square brackets h equals 600 rightwards double arrow open square brackets 72 plus 48 close square brackets h equals 600 rightwards double arrow 120 h equals 600 rightwards double arrow h equals 600 over 120 equals 5 T h u s space h e i g h t space o f space t h e space h a l l space i s space 5 space m.

Answered by Vimala Ramamurthy | 13 Jan, 2015, 11:18: AM

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