03:15Maths ChallengeMaths Challenge 1Complementary additionSchool Radio Duration: 15 minutes Thu 31st May 2012, 03:15 on School RadioAvailable for over a yearListen nowRalph van Dijk and side-kick Matrix have more questions to consolidate mental maths skills and the focus today is Complementary addition.GenresLearningPrimaryBrandMaths ChallengeSeriesMaths Challenge: Maths Challenge 1 Source: BBC Online