# IMO Level 1- Mathematics Olympiad (SOF) Class 10: Questions 639 - 646 of 968

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## Question number: 639

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MCQ▾

### Question

If ‘a’ is the A. M. of 3 numbers and ‘b’ is the A. M. of their squares, then the A. M. of their pair-wise products in terms of a and b is ________

### Choices

Choice (4)Response

a.

b.

c.

d.

## Question number: 640

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MCQ▾

### Question

The value of is ________

### Choices

Choice (4)Response

a.

420

b.

210

c.

195

d.

390

## Question number: 641

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MCQ▾

### Question

If four numbers are in A. P. such that their sum is 90 and the greatest number is 4 times the least, then the numbers are ________

### Choices

Choice (4)Response

a.

b.

c.

d.

Question does not provide sufficient data or is vague

## Question number: 642

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MCQ▾

### Question

Between the numbers 7 and 70,28 means are inserted, then their sum is ________

### Choices

Choice (4)Response

a.

1795

b.

1078

c.

1695

d.

1895

## Question number: 643

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MCQ▾

### Question

In an A. P, If it is given that then is equal to ________

### Choices

Choice (4)Response

a.

b.

c.

d.

## Question number: 644

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MCQ▾

### Question

The value of is ________

### Choices

Choice (4)Response

a.

b.

c.

d.

## Question number: 645

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MCQ▾

### Question

If up to n terms and n is even, then S equals________

### Choices

Choice (4)Response

a.

b.

c.

d.

## Question number: 646

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MCQ▾

### Question

Let denotes the sum of n terms of an A. P. , whose first term is a. if the common difference d is given by then K is equal to ________ ________

### Choices

Choice (4)Response

a.

4

b.

1

c.

3

d.

2

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