This question should be wrong. Because two people use the umbrella of 1, and the umbrella of 10 is enough for five people.

According to mathematical logic, the formula should be, 2 people/umbrella, 5 people is 5÷2=2.5, but there is no half umbrella, so it is 3 umbrellas.

But the title says there are 10 umbrellas, enough for five people. According to the truth, it should be five umbrellas, enough for 10 people.