麻豆约拍

At the South Pole Dave and some penguins explore the operation of plus and the inverse of calculations when adding together two-digit numbers. Two penguins are balancing on an iceberg wearing the signs 'plus' and 'equals'. First they add together 20 and 30 to make 50. 45 + 32 = 77. The penguins and the calculation are balanced. The inverse of this is seen to work just as well; 48 = 21 + ? and ? + 37 = 69 are worked out. All this goes to prove that penguins are perfectly balanced!