no. of sand grains in 1 truck = 10/0.1 x 10 ^-6=10^8 sand grains total time taken= (10 X 6.02x10^23 x 10 )/10^8= 6.02 x 10^17 min= 6.872 x 10^ 13 years Solution no. of sand grains in 1 truck = 10/0.1 x 10 ^-6=10^8 sand grains total time taken= (10 X 6.02x10^23 x 10 )/10^8= 6.02 x 10^17 min= 6.872 x 10^ 13 years.