Percentage? how many percent will Area increase?#shorts

The price of a book went up from $20 to $25. By how many percent did the price increase?

If side of a square is doubled, how many times its area will be increased?

If each edge of a cube is doubled,(i) how many xx will its surface area increase? (ii) how many xx will its volume increase?

If the diameter of cross-section of a wire is decreased by 5% how much percent will the length be increased so that the volume remains the same?

If the population of a town increased every year by 2.1% of the population at the beginning of that year,in how many years will the total increase of population be 20%

If the side of square is increased by 20% , then how much per cent does its area get increased :