Explanation

Given:

a : b : c = 3 : 4 : 7

We need to find (a + b + c) : c

Step 1: Add the ratios:

3 + 4 + 7 = 14

Step 2: The value of c = 7

Step 3: Form the ratio:

14: 7

Step 4: Simplify:

14 : 7 = 2 : 1

Explanation

5 → 25, so multiplier = 25 ÷ 5 = 5

Second quantity = 8 × 5 = 40

Explanation

Cost of 1 pen = 250 ÷ 5 = Rs. 50

Cost of 8 pens = 50 × 8 = Rs. 400

Explanation

Average of 10 values = 200

Total sum = Average × Number of values

= 200 × 10

= 2000

Sum of 9 values = 1850

10th value = 2000 − 1850 = 150

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