At a supermarket, a certain item has increased from 75 cents per pound to 81 cents per pound. What is the percent increase in the cost of the item?

There was an 8% increase in the cost of the item.

If the price of gas increases from $1.00 per gallon to $1.21 per gallon, what is the percent of increase?

The percent of increase is 21%.

The World Future Society predicts that by the year 2030, airplanes will be able to carry 284 passengers. Today's biggest jets can carry 200 passengers. What will be the percent of increase of airplane passengers?

The percent of increase will be %