# IMO Level 1- Mathematics Olympiad (SOF) Class 10: Questions 405 - 410 of 968

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## Question number: 405

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MCQ▾

### Question

The mean of 20 observations is. if each observation is multiplied by 2, then what is the new mean?

### Choices

Choice (4) Response

a.

30

b.

60

c.

70

d.

50

## Question number: 406

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MCQ▾

### Question

A box contains 40 balls of two different colours, out of which x are black. One ball is drawn at random. If 20 more black balls are put in the box, the probability of drawing a black ball now will be double that of the previous probability of drawing a black ball. Then, the value of x is ________

### Choices

Choice (4) Response

a.

12

b.

10

c.

15

d.

14

## Question number: 407

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MCQ▾

### Question

A Motor maintains an average speed of 70 km/hr while going from P to Q and maintains an average speed of 85 km/hr while coming back from Q to P. the average speed of the motor is ________.

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 408

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MCQ▾

### Question

is three vertices of the parallelogram PQRS. The coordinates of fourth vertex is ________

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 409

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MCQ▾

### Question

Four vertices of a parallelogram taken in order are. What will be the ratio of a and b?

### Choices

Choice (4) Response

a.

b.

1: 9

c.

2: 9

d.

3: 7

## Question number: 410

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MCQ▾

### Question

PQR is an isosceles triangle. If the coordinates of the base are , then the coordinates of the vertex P can be

### Choices

Choice (4) Response

a.

b.

c.

d.

None of the above