a shopkeeper bought a bag of millet, he intends to repack the millet in 40g, 250g, and 750g . determine the least mass in grams of millet that was in the bag

Answer 1

40 = 2^3 5^1
250 = 2^1 5^3
750 = 2^1 3^1 5^3
LCM(40,250,750) = 2^3 3^1 5^3 = 3000
So, a 3kg bag will fill 75 40g bags, or 12 250g bags, or 4 750g bags
Or, a 1040g will fill one of each bag.
It's not clear just what it is you want to do.

Remember, It's not my job to figure out what you mean.
It's your job to say it so clearly you cannot be misunderstood.