Which term of the A.P. 18, 15, 12, ………… is the first negative term ?

1. 6^th

2. 8^th

3. 7^th

4. 5^th

The mean proportion between $\dfrac{x - y}{x + y} \text{ and } \dfrac{x^2y^2}{x^2 - y^2}$ is :

1. $\dfrac{xy}{x + y}$

2. $\dfrac{xy}{x - y}$

3. $\dfrac{x - y}{xy}$

4. $\dfrac{x + y}{xy}$

A thick card-board is cut into the shape as shown alongside. It is given a full round about its line of symmetry (shown by dotted line). The solid so formed has :

(i) one cone and one cylinder

(ii) two cones only

(iii) two cones and one cylinder

Which of the statements given above is true ?

1. only (i)

2. only (iii)

3. only (ii)

4. (ii) and (iii)

The probability of answering a question correctly is $\dfrac{2}{5}$ and probability of not answering the same question correctly is $\dfrac{x}{15}$. The value of x is :

1. 6

2. 9

3. 15

4. 5