Find the number that makes the ratio equivalent to 15:6.90:

To find the number that makes the ratio equivalent to 15:6.90, we first need to simplify the given ratio.

The ratio 15:6.90 can be simplified by dividing both numbers by their greatest common divisor. In this case, the greatest common divisor is 1.5.

So, divide 15 by 1.5, which gives 10. Then, divide 6.90 by 1.5, which gives 4.6.

So, the simplified ratio is 10:4.6.

Now, to find the number that makes this ratio equivalent, we need to find a number that when multiplied with both parts of the ratio, gives the original ratio of 15:6.90.

Let's denote this number as x.

So, we have the equations:

10x = 15 and 4.6x = 6.90.

Solving these equations for x gives:

x = 15/10 = 1.5 and x = 6.90/4.6 = 1.5.

So, the number that makes the ratio equivalent to 15:6.90 is 1.5.