Answer:
7 cm by 9 cm
Step-by-step explanation:
The sum of the dimensions is half the perimeter, so is 16 cm. This means you're looking for factors of 63 that have a sum of 16.
Your knowledge of times tables helps you remember that 63 = 7×9. As it happens, those factors have a sum of 16.
The playing card is 7 cm by 9 cm.
