Final answer:
To solve the proportion (r)/(2.8)=(1.8)/(2.1), cross-multiply the fractions and solve for the variable r. The value of r is 2.39.
Step-by-step explanation:
To solve the proportion, cross-multiply the fractions and solve for the variable r.
The proportion given is: (r)/(2.8) = (1.8)/(2.1)
Cross-multiplying gives: 2.1 * r = 2.8 * 1.8
Dividing both sides by 2.1, we get: r = (2.8 * 1.8) / 2.1
Simplifying further, r = 2.39