Advertisements
Advertisements
Question
Find the value of n if `1/(8!) + 1/(9!) = "n"/(10!)`
Advertisements
Solution
`1/(8!) + 1/(9!) = "n"/(10!)`
`1/(8!) + 1/(9 xx 8!) = "n"/(10 xx 9 xx 8!)`
Multiplying thrughout by 8!
`1 + 1/9 = "n"/(10 xx 9)`
`(9 + 1)/9 = "n"/(10 xx 9)`
`"n"/(10 xx 9) = 10/9`
n = `10/9 xx 10 xx 9`
= 100
⇒ n = 100
APPEARS IN
RELATED QUESTIONS
A coin is tossed 3 times and the outcomes are recorded. How many possible outcomes are there?
A Signal is generated from 2 flags by putting one flag above the other. If 4 flags of different colours are available, how many different signals can be generated?
How many numbers between 100 and 1000 have 4 in the units place?
A Signal is generated from 2 flags by putting one flag above the other. If 4 flags of different colours are available, how many different signals can be generated?
How many three-digit numbers can be formed from the digits 0, 1, 3, 5, 6 if repetitions of digits are not allowed?
In a test, 5 questions are of the form 'state, true or false'. No student has got all answers correct. Also, the answer of every student is different. Find the number of students appeared for the test.
Answer the following:
A hall has 12 lamps and every lamp can be switched on independently. Find the number of ways of illuminating the hall.
There are 3 types of toy car and 2 types of toy train available in a shop. Find the number of ways a baby can buy a toy car and a toy train?
How many two-digit numbers can be formed using 1, 2, 3, 4, 5 without repetition of digits?
Three persons enter into a conference hall in which there are 10 seats. In how many ways they can take their seats?
How many three-digit numbers are there with 3 in the unit place?
without repetition
How many three-digit odd numbers can be formed by using the digits 0, 1, 2, 3, 4, 5? if the repetition of digits is not allowed
How many numbers are there between 1 and 1000 (both inclusive) which are divisible neither by 2 nor by 5?
Find the number of ways of distributing 12 distinct prizes to 10 students?
Find the value of 4! + 5!
Find the value of 3! – 2!
Find the value of `(12!)/(9! xx 3!)`
Evaluate `("n"!)/("r"!("n" - "r")!)` when n = 6, r = 2
Out of 18 points in a plane, no three are in the same line except five points which are collinear. Find the number of lines that can be formed joining the point
