Afive digit number is divisible by 3 if the sum of its digits is divisible by 3 proof

Let 10000a+1000b+100c+10d+e be a 5-digit number, where a,b,c,d,e are integers between 0 to 9 inclusively.suppose a+b+c+d+e is divisible by 3.then there exists an integer m such that a+b+c+d+e=3m.then 10000a+1000b+100c+10d+e=9999a+999b+99c+9d+3m=3(3333a+333b+33c+3d+m)since (3333a+333b+33c+3d+m) is an integer, 10000a+1000b+100c+10d+e is divisible by 3.

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.