The average of 20 numbers is 18. The average of the first 10 numbers is 19 and that of the last 9 is 18, then the 11th number is what
Answers
Answer:
18
Step-by-step explanation:
18
Average of 15 numbers = 18
Sum of 15 numbers = 15×18 = 270
Average of first 8 numbers =19
Sum of first 8 numbers = 19×8 =152
Average of last 8 numbers =17
Sum of last 8 numbers =17×8 =136
8th number = Sum of first 8 +Sum of last 8 - total sum
=152+136−270
=18
Answer:
19.5. It does not matter what the first ten numbers are. Since the number three gets added ten times the total sum of the given twenty numbers would increase by 30. Hence add 30 to the previous sum of 360. This results in a sum of 390. Divide this by 20 and voila! You can solve this in yet another way
Mean of 20 numbers= 18
Hence, (Summation of 20 numbers)÷20=18
Now, Mean of 20 numbers after adding three to the first ten numbers,
(Summation of 20 numbers)+(30)÷20
According to distributive law,
Summation of 20 numbers÷20 + 30÷20
Substituting Summation of 20 numbers÷20 = 18
We get,
18+(30÷20)
=18+1.5
=19.5. ANSWER