The number of boys has decreased by 1, so the number of six (1) students is: 1÷(5/9-8/ 15)=45 (people).
2. Let there be x people in the second workshop and (4X/5-30) people in the first workshop.
4x/5-30+10 = 3/4 (x-10), X=250. There are 250 people in the second workshop.
3. Party A walks 2 units less than Party B per hour and 65,438+00 units less than Party B in 5 hours. Two people meet at the midpoint 10km, and Party B walks 20km more than Party A, so 20÷ 10 = 2, and Party B's speed is 2×7 = 14(km/km).
4. Sold 3/4, leaving 1/4. Now the number of books is 2/3, and 200 books are 2/3- 1/4.
The bookstore used to have books on science and technology: 200÷(2/3- 1/4)=480 (this).