12x98

  • Distributive property when one item is close to 100
  • 12(100-2)
  • 1200-24

15x32

  • doubling and halving (halve the even number or lesser of two evens)
  • =30x16
  • =60x8
  • =480

21x21

  • Using “foil”
  • foil 21* 19
  • (20+1) (20-1)
  • 400-20+20-1=399