Explanation

1/3 of 1/2 of 90

= 1/3 × 1/2 × 90

= 1/6 × 90

= 15

Explanation

Total balls = 4 + 5 + 1 = 10

Red balls = 4

Probability = 4/10 = 2/5

Explanation

Numbers in order: 5, 7, 12, 18, 20

Middle value (3rd number) = 12

Explanation

SI = Principal × Rate × Time

= 1000 × 0.05 × 2

= 100

Explanation

Given:

Increment in number = 20% of the number

Decrement in number = 20% of the new number

Concept used:

Net increase or decrease percent = {(Original number or Final number) - (Final number or original number) ÷ Original number} × 100

Calculation:

Let the original number be 100

When the number is increased by 20%

New Number = 100 + 20% of 100

⇒ 100 + 20

⇒ 120

Now, the number is decreased by 20%

Final number = New number – 20% of new number

⇒ 120 – 20% of 120

⇒ 120 – 24

⇒ 96

∴ Net Decrease in percentage = { (100 – 96) / 100} × 100

⇒ {4/100} × 100

⇒ 4%

∴ The net decrease percentage is 4%

Explanation

Initial speed = 90 km/h

Final speed = 72 km/h

Decrease = 90 - 72 = 18 km/h

Percent decrease = (18/90) × 100% = 20%