Multiplication (tables): 5x: starfish

3 - Whiteboard Challenges

Agree or disagree?

Seren said, “I calculated the total number of starfish arms by multiplying 5 by 10 and then adding 5.”

Discuss with your talk partner if you agree with Seren’s method. 

Did you know?

Brittlestars are related to starfish and have a rounded disc-like body with 5 long, thin flexible arms. A brittlestar really does live up to its name as its arms break off very easily when it is attacked. However, this is only a temporary setback as a brittlestar has the power to grow back any lost limbs!

Use Paws and the multiples-of-5 bar to solve the word problem.

Iskra discovered 3 large rock pools on a Cornish beach. In the first rock pool that she looked in, she saw 2 common brittlestars. She saw double this amount in the second rock pool. In the third rock pool, Iskra discovered 6 brittlestars.

If each brittlestar had a complete set of arms, how many brittlestar arms would Iskra be able to count altogether?

Answer: _______________