Question

The intensity of sound wave gets reduced 20% on passing through a slab. What will be the reduction in intensity on passing through two consecutive slabs?

Answer 1

instead of { wo } it must be two
let the intensity of sound be 100
after passing through a slab,
percentage reduced = 20%
amount of intensity reduced = 20% of 100 = 20
remaining intensity = 100 – 20 = 80
after passing through another slab,
intensity of sound = 80
percentage reduction = 20%
amount of intensity reduced = 20% of 80 = 16
remaining intensity = 80 – 16 = 64
total amount of intensity reduced = 100 – 64 = 36
reduction percentage = 36/100 * 100 = 36%

Answer 2

Answer:

ans: 36%

Explanation:

When the sound wave passes through the first slab 20%of its intensity gets reduced, so only ,

100-20= 80% of its intensity is left

Now when it passes through the second slab ,again its intensity gets reduced by 20%

Therefore,

80/100*intensity through first slab

=80/100*80/100

=64/100

64%

therefore 64% of its initial intensity passes and it gets reduced by,

100-64=36%