Page 14 - Digi notes maths

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d. A multiple of 3 or 5

S   1,2,3,4,.. .18,19,20  n   20s 

1.P Mutiple of  3  n  6,3 , 9 , 12 , 15 , 18   6  6
n   s 20 20

2.P Mutiple of  5  n  10,5 , 15 , 20   4
n   s 20

15
3.P Mutiple of 3 and  5  n    1
n   s 20

4.P Mutiple of 3 or  5  n  6,3 , 9 , 12 , 15 , 18 ; 5 ; 10 ; 20   9
n   s 20

8. What is the probability that there will be 53 Sundays in an

ordinary year?

1 Week  7 days
365  52 Complete week means 7 Sundays Confirmed; and 1 odd day

7
This 1 days have Uncertain inty

This 1 day could be (If this 1 day is Sunday the n 53 Sundays would be completed) :

S  Sun ,Mon ,Tue ,Wed ,Thu ,Fri ,Sat  n   7S
E  Sun  n   1E

P  53 Sundays   1
7

9. What is the probability that there will be 53 Sundays in a leap

year?

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