Answer:
a. 9 cm thick
b. 189 sheets
Explanation:
a. 280 sheets = 4cm thick and 630 sheets = ? cm thick
using unitary method
280 x = 4 × 630
x = 9cm
b. 280 sheets = 4cm thick and ? sheets = 2.7 cm thick
using unitary method
280 × 2.7 = 4 x
x = 189 sheets
