Final answer:
The probability that all four pennies will be tails when you and a friend each toss two pennies at the same time is 6.25%.
Step-by-step explanation:
The probability of each penny landing on tails is 50% (or 0.5). Since you and your friend are both tossing two pennies each, that's a total of four pennies. We calculate the probability of all four pennies landing on tails by multiplying the individual probabilities:
Probability for one penny = 0.5
Probability for four pennies = 0.5 × 0.5 × 0.5 × 0.5
Probability for four pennies = 0.0625 or 6.25%
So, the probability that all four pennies will be tails is 6.25%.