Answer:
Step-by-step explanation:
Total 3-digit numbers 100 to 999
3 digit multiples of 5; 100 to 995
- smallest one 100 = 5*20
- greatest one 995 = 199*5
- number 199 - 4 = 195
3 digit multiples of 7:
- smallest one 105/7 = 15
- greatest one 994/7 = 142
- number 142 - 14 = 128
Total multiples of either 5 or 7 :
This number includes multiples of both 5 and 7
We need to exclude half of the multiples of 5*7= 35 as they are counted twice:
- smallest one 105 = 35*3
- greatest one 980 = 28*35
- number 28 - 2 = 26
Half of this is 26/13 = 13
The difference of 900 and 310 is the answer:
