Well 10.00 ÷ 0.30 is hard to do, so an easier way is to go 10.00 ÷ 0.50 = 20. Another way it to go 10.00 ÷ 0.25 = 40. The number of cupcakes has to be between 20-40.
Let's say you and 3 friends have to divide orange juice, there's 1.36 liters. How much will each friend get? Estimate then calculate.
1.36 ÷ 4, that's too hard to do so lets just say 1.50 ÷ 4 = 0.375, you can also do 1.30 ÷ 4 = 0.325. Another way is 1.2 ÷ 4 = 0.3 and 1.6 ÷ 4 = 0.4 so the answer has to be around 0.3-0.4.
Here is a video that might make dividing decimals easier
Also here is a link to a fun game for dividing decimals!