Answer:
1 
Step-by-step explanation:
Note there is a common ratio between consecutive terms, that is
10 ÷ 20 = 5 ÷ 10 = 2
÷ 5 = 
Thus to obtain the next term in the sequence multiply the previous term by 
2
×
= 1 
Answer:
3
Step-by-step explanation:
If 6 numbers have a mean value of 10, it means that the sum of the numbers divided 6 is equal to 10. This can be expressed as:
x÷6=10
x=60
The new number added will be the 7th number and now the mean is 9. You have to ask what number divided by 7 is equal to 9? This can be expressed as:
y÷7=9
y=63
63-60=3
So the new number added is 3
Answer: Irrational
Step-by-step explanation: