If the base of a triangle increases by 10% and the height decreases by 10%, the area of the triangle () A. Increase by 0.5% B. decrease by 1% C. increase by 1% d. no change

If the base of a triangle increases by 10% and the height decreases by 10%, the area of the triangle () A. Increase by 0.5% B. decrease by 1% C. increase by 1% d. no change

According to the area formula of the triangle, the area of the triangle is: 1.1 bottom × 0.9 height △ 2 = 0.99 (bottom × height △ 2), which is 1% less than the original triangle

1. A rectangle is 42 cm long and 20 cm wide. Cut out the largest triangle from the rectangle. What is the area of the triangle?

42 × 20 △ 2 = 420 (square centimeter)

If the three sides of a triangle are 15 cm, 20 cm and 25 cm long, then the area of the triangle is

The ratio of the three sides of the triangle
=15：20：25
=3：4：5
So, this is a right triangle
The sides 15 and 20 cm long are right angles
Its area
=15×20÷2
=150 (square centimeter)

It is known that the three sides of a triangle are 12cm, 16cm and 20cm respectively. Can you calculate the area of the triangle?

∵ 122 + 162 = 202, ∵ triangle is a right triangle, s = 12 × 12 × 16 = 96cm2