Add numbers from left to right when dealing with the addition of two numbers. Regroup the numbers in your head, after you have added them from left to right, to account for the carrying of numbers. Add the numbers 2,167 to 9,237 from the left to get 11 + 3 + 9 + 14. Regroup the numbers to reach the sum of 11,404.
Find the answers to long columns of addition by grouping the numbers in each column into sums of 10. Combine 3s with 7s, 8s with 2s, 9 with 1s, and 5s with 5s. Add all of the groups of 10 together, and then add the outlying numbers in. Account for carrying after both columns are added.
Multiply from left to right. Multiply the numbers 25 and 49 by multiplying the 2 and the 4, then the 2 and the 9. Add the two numbers together from left to right: 8 + 18 = 98. Multiply the 5 and 4 to get 20, and add it to 98 to get 118. Multiply 5 times 9 last, add two 0s to the front of 45, then add it to 118, from left to right, to get the final answer of 1,225.
Practice mental math to get the hang of it. Check your answers by hand or with a calculator when you first start learning to do speed math.
Pick up on math tricks to increase your speed. Multiply numbers by 10, then divide them by 2 when multiplying by 5. Multiply a number by 3, and then multiply the answer by 2 when multiplying by 6. Dissect numbers in as many simple ways as possible, and then combine the answers for a speedy result.