If a given 3 digit number is a multiple of 7, we need to find the probability of it being a multiple of 5.

1. Probability Q3

2. Qn: Probability
(a)
1
5
(b)
11
54
(c)
13
64
(d)
13
66
N is a 3-digit number that is a multiple of 7; what is the probability
that it will be a multiple of 5?

3. Soln: Probability
N is a three digit multiple of 7.
N could be 105, 112, 119, 126…..994.
Or, 15 × 7, 16 × 7…..142 × 7.
Or there are 142–14 = 128 numbers.
Within these we need to locate the multiples of 5.
Or, we need to isolate multiples of 35.
Or, we need to see how many numbers there are in the list 105, 140,
175…..980.
N is a 3-digit number that is a multiple of 7; what is the probability
that it will be a multiple of 5?

4. Soln: Probability
35 × 3, 35 × 4…35 × 28…
Or, there are 26 such numbers.
Probability
26
128
=
13
64
Answer choice (c)
N is a 3-digit number that is a multiple of 7; what is the probability
that it will be a multiple of 5?