# IGCSE Mathematics Paper-1: Specimen Questions with Answers 276 - 281 of 324

## Question 276

### Explanation

- A prime number is a whole number greater than 1 whose only factors are 1 and itself.
- In this number is prime number
- Because
- And 2 is a prime number.

## Question 277

## Question 278

## Question 279

Edit

### Write in Short

Short Answer▾Look at the sequence of diagrams above.

The number of dots in each diagram is given in the table below.

Find the number of dots in

Diagram 50,

### Explanation

For this sequence the diffrence between each diagram and next diagram is 3.

Here

Here apply this equaion

The number of dots in 50^{th} diagram is 160.

## Question 280

### Explanation

- The perimeter is Where r is the radius and d is the diameter Here it is a semicircles, that is half the circle is the perimeter Here