Justin rode his bicycle 2.1 miles a day for 16 days straight. how many miles did Justin ride altogether during the 16 day stretch?

International calls require the use of a country code. many country codes a 3-digit numbers. country codes do not begin with a 0 or 1. there are no restrictions on the second and third digits. how many different 3-digit country codes are possible?

What is the total surface area of this square pyramid?

If t17 = 3 (t5) in an arithmetic progression, find t1 in terms of d.