Basic Mathematics

A number is increased by 20% and then decreased by 20%. The net change is:
‎a) No change
b) 4% increase
‎c) 4% decrease
d) 20% decrease

The ratio of angles of a triangle is 2:3:4. The largest angle is:
‎a) 40° ‎ b) 60°
‎c) 80° ‎d) 100°

If the perimeter of a square is 36 cm, its area is:
‎a) 72 cm² ‎b) 81 cm²
‎c) 64 cm² ‎d) 100 cm²

The sum of a number and its square is 20.The number is:
‎a) 4 b) –5
‎c) 5 d) –4

If
‎2 ★ 3 = 11
‎3 ★ 4 = 19
‎4 ★ 5 = 29
‎Then the value of ‎5 ★ 6 = ?
‎a) 39 b) 41
c) 43 d) 45

If
2 ★ 3 = 11
3 ★ 4 = 19
4 ★ 5 = 29
Then the value of
5 ★ 6 = ?
a) 39 b) 41
c) 43 d) 45

A number when added to its square gives 42. Find the number?