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%.

Last verified on 11-07-2026

Explanation

Given:

Average of 5 numbers = 4

2 is added to each number.

Formula:

Average = Sum of numbers ÷ Number of numbers

Original Sum = 4 × 5 = 20

After adding 2 to all 5 numbers:

New Sum = 20 + (2 × 5) = 30

New Average = 30 ÷ 5 = 6

Explanation

• Speed = 12 km/h
• Time = 15 minutes = 15/60 = 1/4 hour

Formula:

Distance = Speed x Time 

= 12 x 1/4

$$= 12 times frac{1}{4}$$ =3 km

Explanation

Average=Sum of numbersNumber of numbers​

So:

Sum =Average× Number of numbers

= 33 x 3 

= 99
​

Explanation

15% of 240 = (15/100) × 240

= 0.15 × 240 = 36

Last updated by NA on 24-April-2026