Explanation

• Let r be the radius of a circle.
• Then, the area of the circle = πr^2 
• If radii are doubled, than radii become 2r.
• Now, area of circle =π(2r) 2
•  =4π.
• Therefore, the area of the circle is increased by 4 times.

Explanation

• Al-Khwarizmi is known as the Father of Algebra for writing the first systematic book on algebra.
• He wrote Al-Kitab al-Mukhtasar fi Hisab al-Jabr wal-Muqabala in the 9th century.
• The word “Algebra” comes from “Al-Jabr” in his book title.

Last verified on 24-06-2026

Explanation

Explanation

Total students = 27

Since 7 more girls than boys, let's represent the number of boys as x.

Number of girls = x + 7

Total students = Boys + Girls

27 = x + (x + 7)

Combine like terms:

27 = 2x + 7

Subtract 7:

20 = 2x

Divide by 2:

10 = x

Number of boys = 10

Number of girls = 10 + 7 = 17

Therefore:

Total girls in the class = 17

Last verified on 06-03-2026

Explanation

80 percent of 700 is 560.

80 percent *700

= (80/100)*700

= (80*700)/100

= 56000/100 = 560

Explanation

A and B together can complete the work in 3 days, so their combined rate of work is 1/3 per day.

They work together for 2 days, so they complete 2/3 of the work.

B leaves, and A completes the remaining 1/3 of the work in 2 days. This means A's rate of work is 1/6 per day (since A completes 1/3 of the work in 2 days).

Now, we know B's rate of work is the difference between their combined rate and A's rate: (1/3 - 1/6) = 1/6 per day.

Since B can complete the entire work in x days, B's rate of work is also 1/x per day.

Equating the two expressions for B's rate of work, we get: 1/6 = 1/x --> x = 6

So, B alone can complete the work in 6 days.

Explanation

Step 1: Multiply the number of students in each class by their pass percentage

- Class 1: 10 students × 20% = 2 passed  

- Class 2: 20 students × 30% = 6 passed  

- Class 3: 30 students × 60% = 18 passed  

- Class 4: 40 students × 100% = 40 passed  

Step 2: Add total passed students and total students

- Total passed = 2 + 6 + 18 + 40 = 66  

- Total students = 10 + 20 + 30 + 40 = 100

Step 3: Calculate the overall percentage

Pass % = (66 / 100) × 100 = 66%

Explanation

1 kilometre is equal to 1000 metres.

Explanation

Total students = 95  

Girls = 45  

So, Boys = 95 - 45 = 50

Ratio of boys to girls = 50 : 45

Simplify by dividing both by 5:

= 10 : 9

Explanation

- 9 - x = ?

- 25 - 9 = 16  

- 48 - 25 = 23  

- 81 - 48 = 33  

- 121 - 81 = 40  

Now look at the differences: 16, 23, 33, 40

Now check differences of differences:

- 23 - 16 = 7  

- 33 - 23 = 10  

- 40 - 33 = 7  

There’s a slightly alternating pattern in second differences: 7, 10, 7...

Assuming this pattern continues backward, before 16, we should subtract 10 (alternating) ⇒ 16 - 10 = 6

So:  

9 - x = 6 ⇒ x = 3