Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?
Can you find out which options fits best with the missing column?
Can you place three balls such that the equation shown in the picture holds true?
Can you solve the maths in the below-given picture equation?
