Answer :
There are 210 sequences for 7 church bells to rung with the given conditions. Using permutations, the required number of sequences is calculated.
What are permutations?
A sequence or arrangement that can be framed by taking some or all of a finite set of things (or objects) is called a permutation.
The formula for finding the number of such arrangements is,
ⁿPₓ = n!/(n - x)!
Calculation:
It is given that, a church's bell tower has 7 bells. 3 of them will ring in a sequence before each service and no bell is rung more than once.
So, the number of sequences that the bells will form is calculated by using the permutations formula. I.e., ⁿPₓ = n!/(n - x)!
Here, n = 7; x = 3
Then,
ⁿPₓ = n!/(n - x)! ⇒ ⁷P₃ = 7!/(7 - 3)! = 7!/4!
⇒ ⁷P₃ = (7 × 6 × 5 × 4!)/4! = 7 × 6 × 5 = 210
Therefore, there are 210 sequences for ringing the bells.
Learn more about permutations here:
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