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

Explanation

Given:

• Average weight of 5 persons = 60 kg
• New average of 6 persons = 62 kg

Step 1: Total weight of 5 persons

5 × 60 = 300kg

Step 2: Total weight of 6 persons

6 x 62 = 372kg

$$6 times 62 = 372text{ kg}$$

Step 3: Weight of the new person

$$=\; 372-300$$

=72 kg​

Explanation

Given ratio:

Copper : Silver = 3 : 5

Step 1: Find the total parts:

3+5=8

Step 2: Silver represents 5 parts out of total 8 parts.

Fraction of Silver = Silver parts/Total parts

=5/8

$$\text{<br>}$$$$=frac{5}{8}$$

Explanation

Given:

a:b = 8:9,

b:c = 6:5

Make b equal in both ratios. LCM of 9 and 6 = 18.

a:b=8:9=16:18

b:c=6:5=18:15

So, a:b:c = 16:18:15