At a two-day seminar, 90 percent of those registered attended the seminar on the first day. What percent of those registered did not attend the seminar on either day?

(1) A total of 1,000 people registered for the two-day seminar. (2) Of those registered, 80 percent attended the seminar on the second day.

30%

Step-by-step explanation:

Total number of people registered for the two days seminar = 1000

90% of those registered attended on the first day

This means (90/100) 1000 = 900 people attended the seminar on the first day.

That means 100 (1000 - 900) registered people did not attend the seminar on the first day

80% of those registered attended on the second day

This means (80/100) 1000 = 800 people attended the seminar on the second day.

That means 200 (1000 - 800) registered people did not attend the seminar on the second day

The percent of those registered did not attend the seminar on either day = 100 + 200 = 300

= 30%

Total = Group A + Group B - (both + neither)

1000 = 900 + 800 - (B + N)

The two unknown variables (both and neither)