Four friends contributed money in the ratio 2:4:5:7.If the largest amount contributed was $1.40, calculate the total amount contributed by all four people?

Let's assume the smallest ratio unit is x.

The ratio given is 2:4:5:7.

So, if the largest amount contributed is $1.40, it corresponds to the ratio unit 7x.

Now, we can set up a proportion to find the value of x:

7x / 1.40 = 1 / 1

To isolate x, we can cross-multiply:

7x = 1.40 * 1

7x = 1.40

Now, divide both sides of the equation by 7 to solve for x:

x = 1.40 / 7

x = 0.20

Therefore, the value of the smallest ratio unit (x) is $0.20.

To find the total amount contributed by all four people, we need to add up the amounts contributed by each person.

Person 1 contributed 2 units, so the total amount contributed by Person 1 is 2 * $0.20 = $0.40

Person 2 contributed 4 units, so the total amount contributed by Person 2 is 4 * $0.20 = $0.80

Person 3 contributed 5 units, so the total amount contributed by Person 3 is 5 * $0.20 = $1.00

Person 4 contributed 7 units, so the total amount contributed by Person 4 is 7 * $0.20 = $1.40

Now, to find the total amount contributed by all four people, we add up the amounts:

Total amount contributed = $0.40 + $0.80 + $1.00 + $1.40 = $3.60

Therefore, the total amount contributed by all four people is $3.60.