Chapter 6 - Percent - 6.1 Basics of Percent - 6.1 Exercises - Page 387: 57

270

If we need 300% of the chairs used last week for this week's meeting, this means that we need three times as many chairs this week as the amount of chairs used last week. Therefore, we need $3\times90=270$ chairs. 300%$=300\div100=3$ $90\times3=270$ chairs