We can figure out how many times a heart beats in one minute (so we can figure out how many minutes it will take for 140 times) by dividing 700 by 10. This gives us 70. Now we know that a heart beats 70 times each minute. Now we know it would take 2 minutes for a heart to beat 140 times because 70×2=140.
Two minutes is the answer.
If 2 boxes remain empty, it means that we put all three balls in one single box.
Suppose the full box is box number 1. For each ball, we have three choices - we may put it in box number 1, 2 or 3. This means that each box has a 1/3 chance of receiving each ball.
So:
- we choose box 1 for ball 1 - that's a 1/3 chance
- we choose box 1 for ball 2 - that's a 1/3 chance
- we choose box 1 for ball 3 - that's a 1/3 chance
So, the probability of putting all balls in box 1 is
![\dfrac{1}{3}\times\dfrac{1}{3}\times\dfrac{1}{3} = \dfrac{1}{3^3}](https://tex.z-dn.net/?f=%20%5Cdfrac%7B1%7D%7B3%7D%5Ctimes%5Cdfrac%7B1%7D%7B3%7D%5Ctimes%5Cdfrac%7B1%7D%7B3%7D%20%3D%20%5Cdfrac%7B1%7D%7B3%5E3%7D%20)
But this is the probability of putting all ballx in box 1, and you can repeat this logic for box 2 and 3.
So, the probability of putting all balls in one single box is 1/27 for each box, for a total of
![\dfrac{1}{27} \times 3 = \dfrac{1}{9}](https://tex.z-dn.net/?f=%20%5Cdfrac%7B1%7D%7B27%7D%20%5Ctimes%203%20%3D%20%5Cdfrac%7B1%7D%7B9%7D%20)
Answer:d
Step-by-step explanation: