Find the area of the rhombus, one of the diagonals is 28 cm, and the second diagonal is 40% larger than the first.

Let’s calculate the length of the second diagonal of the rhombus. Let’s compose the proportion in which the first diagonal is equal to 100%:
28 centimeters – 100%,
x centimeters – 140%.
Let’s solve the proportion and find the unknown x:
x centimeters = 28 centimeters * 140%: 100% = 39.2 centimeters.
The second diagonal is 39.2 centimeters long.
The area of a rhombus is found by the formula:
S = d1 * d2: 2, where d1, d2 are the diagonals of the rhombus:
Let’s substitute our values:
S = 28 centimeters * 39.2 centimeters: 2 = 548.8 cm².
Answer: the area of the rhombus is 548.8 cm².