How to find the average of first 20 multiple of 7?

Find the average of first 10 multiples of 7
35.5
37.5
38.5
40.5
Answer: Option C
Explanation:
=7(1+2+3+...+10)10
=7(1+2+3+...+10)10


=7(10(10+1))10×2
=7(10(10+1))10×2


=7(110)10×2=38.5
=7(110)10×2=38.5
Similar Questions :
1. The average of four consecutive odd numbers is 24. Find the largest number.
25
27
29
31
Answer: Option B
Explanation:
Let the numbers are x, x+2, x+4, x+6, then
=>x+(x+2)+(x+4)+(x+6)4=24
=>x+(x+2)+(x+4)+(x+6)4=24


=>4x+12)4=24
=>4x+12)4=24


=>x+3=24=>x=21
=>x+3=24=>x=21


So largest number is 21 + 6 = 27
2. Average age of boys in a class is 16 years and average age of girls is 15 years, what is the average age of all
15.5
15
16
Cant be computed
Answer: Option D
Explanation:
As number of girls and boys is not given so result cant be computed
3. Average of five numbers is 27. If one number is excluded the average becomes 25. The excluded number is
35
45
55
65
Answer: Option A
Explanation:
Number is (5*27) - (4*25) = 135-100 = 35
4. A batsman makes a score of 87 runs in the 17th match and thus increases his average by 3. Find his average after 17th match
36
37
38
39
Answer: Option D
Explanation:
Let the average after 17th match is x
then the average before 17th match is x-3

so 16(x-3) + 87 = 17x
=> x = 87 - 48 = 39
5. Average of 10 matches is 32, How many runs one should should score to increase his average by 4 runs.
70
76
78
80
Answer: Option B
Explanation:
Average after 11 innings should be 36

So, Required score = (11 * 36) - (10 * 32)
= 396 - 320 = 76