Tính :
a) 645 × (30 – 6 ) = ………………………
= ………………………
= ………………………
278 × (50 – 9) = ………………………
= ………………………
= ………………………
b) 137 × 13 – 137 × 3 = ………………
= …………………
= …………………
538 × 12 – 538 × 2 = ………………
= …………………
= …………………
a) 645 × (30 – 6) = 645 × 30 – 645 × 6
= 19350 – 3870
= 15480
278 × (50 – 9) = 278 × 50 – 278 × 9
= 13900 – 2502
= 11398
b) 137 × 13 – 137 × 3 = 137 × (13 – 3)
= 137 × 10
= 1370
538 × 12 – 538 × 2 = 538 × (12 – 2)
= 538 × 10
= 5380
-- Mod Toán lớp 4