39,511 when rounded to the nearest thousand equals too...
40,000
5:7 (pencils to pens)
7/12 chance that a pen from the first box will be selected.
4:4 (colour pencils to crayons)
4/8 = 1/2 chance that a crayon from the second box will be selected.
The probability of picking both:
7/12 * 1/2 = 8/24 = 1/3
I believe the answer is 8
If we made it into a ratio of residential customers to business customers, it would be a 2:1
350/2 = 175
350 + 175 = 525
525 total customers