A bacteria colony of 100 cells doubles every 3 hours. How many cells are there after 12 hours?
Answer and explanation
Correct answer: D. 1600
- Step 1: 12 hours contain 12/3 = 4 doublings.
- Step 2: 100 x 2^4 = 1600.
Answer
1600.
Why not the others: Doubling means multiplying by 2 each period, not adding a fixed amount; counting one doubling per hour gives far too many.
Practise more Percentages, ratios and averages.
Free questions with an explanation for every one, and full timed Psychometric Entrance Test (PET Israel) mock tests.
More Percentages, ratios and averages questions
- A jacket costs 300 shekels. It is sold at a 25% discount. What is the sale price in shekels?
- 55 marbles are divided between two children in the ratio 4:7. How many marbles does the child with the larger share get?
- 6 liters of a 30% salt solution are mixed with 4 liters of a 60% salt solution. What is the salt concentration of the mixture?
- 5000 shekels are invested for 2 years at 10% compound interest per year. What is the amount after 2 years?
- A price of 80 is increased by 40% and the new price is then reduced by 50%. What is the final price?
- A jacket costs 500 shekels. It is sold at a 40% discount. What is the sale price in shekels?