There are 100 bulbs and 100 switches.Each switch is numbered from 1 to 100 and each switch corresponds to each bulb. (a)all switches are switched on. (b)the switch nnumberes which are divisible by 2 are marked and those switches which are on are put off and which are off are put on. (c)the switch numbers which are divisible by 3 are marked and those switches which are on are put off and which are off are put on. (d)this process continued till the number 100. By the end how many switches are glowing.?
ANS "0" (even the question is wrong , switches cant glow. but if q. was right probably that would still be the right ans.)
first of all , read the question properly..
all 100 switches are switched on.
then switches 2,4,6....100 are "MARKED"( but not switched "OFF") , then all the bulbs which are glowing are switched off, i.e " ALL THE 100 BULBS WHICH ARE GLOWING ARE SWITCHED OFF".
in the next step again all that are switched off are switched on , THUS AT THE END ALL 100 BULBS ARE SWITCHED "OFF" , coz bulbs remain off for even numbers and on for odd numbers..
RE: There are 100 bulbs and 100 switches.Each switch i...
Question: There are 100 bulbs and 100 switches.Each switch is numbered from 1 to 100 and each switch corresponds to each bulb. (a)all switches are switched on. (b)the switch nnumberes which are divisible by 2 are marked and those switches which are on are put off and which are off are put on. (c)the switch numbers which are divisible by 3 are marked and those switches which are on are put off and which are off are put on. (d)this process continued till the number 100. By the end how many switches are glowing.?
RE: There are 100 bulbs and 100 switches.Each switch i...
I think we can solve this problem this way.
I you take a few examples (any number) we will find that it is switched on/off only odd number of times(excluding dividing by 1 and including dividing the number by itself).
Thus as the initial condition is ON so we have all of them switched OFF; except for the perfect squares as they have ONE MORE NUMBER to divide them
ie the Suare Root of that number. so they are switched off/on even number of times. So 10(1 4 9 16 25 36 49 64 81 and 100) remains switched ON.
RE: There are 100 bulbs and 100 switches.Each switch i...
ANS 0 (even the question is wrong switches cant glow. but if q. was right probably that would still be the right ans.)
first of all read the question properly..
all 100 switches are switched on.
then switches 2 4 6....100 are MARKED ( but not switched OFF ) then all the bulbs which are glowing are switched off i.e ALL THE 100 BULBS WHICH ARE GLOWING ARE SWITCHED OFF .
in the next step again all that are switched off are switched on THUS AT THE END ALL 100 BULBS ARE SWITCHED OFF coz bulbs remain off for even numbers and on for odd numbers..
RE: There are 100 bulbs and 100 switches.Each switch is numbered from 1 to 100 and each switch corresponds to each bulb. (a)all switches are switched on. (b)the switch nnumberes which are divisible by 2 are marked and those switches which are on
Yes the answer is '0'
Regarding statement B It is said that the switch numbers are divisible by 2 are marked and those switches which are on are put off and which are off are put on we get that all the switches are off from the above step.
For every marking of even number all the switches get off
so as 100 is an even number all the switches get off
so 0 bulbs glow (switches glow may not be technically correct).
RE: There are 100 bulbs and 100 switches.Each switch is numbered from 1 to 100 and each switch corresponds to each bulb. (a)all switches are switched on. (b)the switch nnumberes which are divisible by 2 are marked and those switches which are on
Switch numbers which are perfect squares will be on. This is because perfect squares have odd number of factors. eg: 9 factors are 1 3 9 25 factors are 1 5 25
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