The mean age of a group of students is 16. John joins the group and the mean age changes to 18. How old is john ?
1 answer:
Answer:
John is 20 years old.
Step-by-step explanation:
Given the second mean is 18, it is equal to the first mean age plus John's unknown age. The sum is also divided by 2 because there are 2 values in the sum (1. John's age and 2. the mean, 16 yrs old).
Set up an equation:
multiply both sides by 2:
simplify:
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Answer:
There will be 200 000 bacteria after 8 hours
Step-by-step explanation:
The crop quadruples every hour.
x represents the number of hours that pass after preparing the crop
y represents the number of bacteria after x hours.
The equation for y in function of x 3 hours after observing the crop is:
We want to know after how long there will be 200 000 bacteria.
Then we make y = 200 000 and clear x.