A ribbon was cur into twi pieces in the ratio of 3:7. If the shorter ribbon is 21 meters, how long is the longer one?

3x = 21

x = 7
7x = 49

To find the length of the longer ribbon, we need to determine the ratio of the lengths of the two pieces. Given that the shorter ribbon is 21 meters, let's use a variable "x" to represent the length of the longer piece.

The ratio of the lengths is given as 3:7, which means that the length of the shorter ribbon is 3 out of the total 10 parts, and the longer ribbon is 7 out of the total 10 parts.

We can set up a proportion to find the length of the longer ribbon:

(Length of shorter ribbon)/(Length of longer ribbon) = (Ratio of lengths in terms of parts)/(Total parts)

21/x = 3/7

To solve this proportion, we can cross-multiply:

3x = 7 * 21

Multiply:

3x = 147

Now, we isolate "x" by dividing both sides of the equation by 3:

x = 49

Therefore, the length of the longer ribbon is 49 meters.