As they given the values in the picture, You observe the option A. Add 7.4cm two times because it's opposite side is equal. You'll get 14.8cm and add 12.3cm two times you'll get 24.6cm Add 12.3cm and 24.6cm you'll get 39.4cms as answer.
Observe the option C. Add 9.8 two times because it's opposite side is equal. You'll get 19.6. Add 9.9cm two times, you'll get 19.8cm. Add 19.6 and 9.9cm, you'll get 39.4cms as answer.
