View written solutionFree
Correct answer: 125
We need the number of ordered outcomes when a die is thrown 4 times such that where each .
Step 1: Convert to a nonnegative integer equation
Let Then each and , and
So we need the number of nonnegative integer solutions of with the restriction .
Step 2: Count all nonnegative solutions without the upper bound
Ignoring the condition , the number of nonnegative solutions is
Step 3: Subtract solutions where at least one variable exceeds 5
We now subtract cases where some .
For a particular variable, say , write Then Number of solutions:
There are 4 choices for which variable is at least 6, so total to subtract initially:
Step 4: Add back intersections
If two variables are both at least 6, say , then let This gives So there is exactly solution for each such pair.
Number of pairs: So we add back
Step 5: Higher intersections
Three variables cannot each be at least 6, because that would require sum at least . So no further terms occur.
Step 6: Final count
By inclusion-exclusion,
Therefore, the number of ways is
More from Permutations and Combinations
- Let the set be partitioned into 3 sets with equal number of elements such that and …2024 · MCQ
- 60 words can be made using all the letters of the word , with or without meaning. If these words are written as in a dictionary, then the word is:2024 · MCQ
- The number of triangles whose vertices are at the vertices of a regular octagon but none of whose sides is a side of the octagon is2024 · MCQ
- If all the words with or without meaning made using all the letters of the word "NAGPUR" are arranged as in a dictionary, then the word at position in this arrangement is :2024 · MCQ
- Let . If , then is equal to :2024 · MCQ
- Let be the greatest integer less than or equal to . Let be the set of all prime factors of 2310 and be the function . The…2024 · MCQ
- The number of 3-digit numbers, formed using the digits 2, 3, 4, 5 and 7, when the repetition of digits is not allowed, and which are not divisible by 3 , is equal to .2024 · Numerical
- The number of ways five alphabets can be chosen from the alphabets of the word MATHEMATICS, where the chosen alphabets are not necessarily distinct, is equal to:2024 · MCQ