00:01
Okay, as per the question is, machine shop has 120 equally noisy machines in that shop, okay? that together produce the intensity level of 92 decibel, okay? if the intensity level must be reduced to 83 decibel, okay, then how many machines must be turned off? that is surely we have to reduce the intensity, okay? so we have to turn off some machines, so we have to find out that.
00:30
So let's say the intensity of one machine is i.
00:34
Intensity of intensity of one machine is i.
00:44
So initially 120 machine produces 92 decibel.
00:48
So we know that the intensity, okay? or we can say the sound that will be 10, log i divided by i note.
00:57
And here 120 machine and one machine is from intensity is i.
01:01
So it will be 120 i divided by i not okay and beta one that is given 92 decibel okay and now we have to turn off some machines so let's say n machines are turned off then the required intensity level it will be 83 and it will be 10 log and now the total machines remaining it will be 120 minus n that is i divided by i not so it is equation one and this is equation one and this is equal 2 and we have to find out the value of n from these two equation that is pretty simple we will subtract equation 1 minus 2 so 92 minus 83 that is 9 okay and it is 10 log 120 i divided by i not minus 10 log 120 minus n i divided by i not okay so now log a minus will be common factor and now log a minus log b that is log a by b okay first of all 10 will be common factor and log a minus log b that is log a by b so it will be log 120 i divided by 120 minus n i okay i not will be cancel out and of course this i also cancel out so 9 by 10 it will be 0 .9 that is equal to log okay and this log having base 10 okay okay okay and it will be 120 divided by 120 minus n...