TÍnh a) 2/3 x 3/4 x 4/5=... b) 8/9 x 9/10 x 10/11=... c) 5/24 x 12/15 x 48/12=...

`a, 2/3 × 3/4 × 4/5`

`= (2×3×4)/(3×4×5)`

`= (2×\cancel(3) × \cancel(4))/(\cancel(3)×\cancel(4) × 5)`

`= 2/5`

`b, 8/9 × 9/10 × 10/11`

`= (8×9×10)/(9×10×11)`

`= (8×\cancel(9) × \cancel(10))/(\cancel(9)×\cancel(10) × 11)`

`= 8/11`

`c, 5/24 × 12/15 × 48/12`

`= (5×12×48)/(24×15×12)`

`= (\cancel(5)×\cancel(12) × \cancel(48))/(\cancel(24)×\cancel(15) × \cancel(12) )`

`= (1 ×1×2)/(1×3×1)`

`= 2/3`

`d, 21/8 × 16/14 × 7/2 × 8/7`

`= (21×16×7×8)/(8×14×2×7)`

`= (\cancel(21)×\cancel(16) × \cancel(7)× \cancel(8))/(\cancel(8)×\cancel(14)×\cancel(2) × \cancel(7) )`

`= (3×8×1×1)/(1×2×1×1)`

`= 24/2`

`= 12`