Speed Math (Idiot's Guides)
Format: PDF / Kindle (mobi) / ePub
Do math more quickly and with more confidence — with less reliance on paper, apps, and calculators. For people who automatically run to the nearest calculator, Idiot's Guides: Speed Math teaches tips, tricks, and straightforward methods to doing math at a fast — and accurate — rate. Practice examples easily illustrate how even the most math-shy person can better perform calculations.
it to the left of the line, with the 7 serving as the flag pole and the 43 serving as the flag. You have two digits in the flag, so put a line two to the left of the dividend to indicate where the decimal point goes. Step 2: Divide 10 by the flag pole, 7. This gives you a quotient of 1 and a remainder of 3 (because 7 × 1 = 7, which is the highest multiple of 7 that can go into 10). Put down 1 and prefix the remainder of 3 to 6 so it becomes 36. Step 3: Subtract 36 by the first digit of the flag
denominator of by 4 to get the fraction you can use. Step 2: Add the numerators of the fractions. Solution: The answer is . Example 2 Solve the problem . Step 1: Because 15 is a factor of 30, multiply the numerator and denominator of by 2 to get the fraction you can use. Step 2: Add the numerators of the fractions. Solution: The answer is . Addition with the Vertically and Crosswise Method To add fractions without a common denominator or one that’s a factor of the other, you can use the
numbers. So 567.29 becomes 56,729 and 45.67 becomes 4,567. Step 2: Divide the numbers. 56729 ÷ 4567 = 12.4215 Solution: The answer is 12.4215. Example 2 Solve the problem 7.625 ÷ 0.923. Step 1: Because the decimal is three places to the right in each number, you shift the decimal points right three places to get the whole numbers. So 7.625 becomes 7,625 and 0.923 becomes 923. Step 2: Divide the numbers. 7625 ÷ 923 = 8.2611 Solution: The answer is 8.2611. Example 3 Solve the problem
next step. Step 9: In the last column, add 1 and the carryover: 1 + 1 = 2. Put down 2. Solution: The answer is 248,832. SPEED BUMP Don’t forget, if the a digit isn’t 1, you can’t simply multiply by b and have your answer; because you’re using the ratio , you have to multiply by b and divide by a. The Least You Need to Know To find out how much a number is to the fourth power, use a4 + a3b + a2b2 + ab3 + b4 and 3a3b +5a2b2 + 3ab3 to find the values, and add right to left. To do fifth power
left side. Solution: The answer is 90,288. SPEED BUMP Unlike in earlier problems involving the base method, simply combining the two parts of the answer won’t yield the correct response. You have to subtract the right side from the left side to get your answer. General Multiplication Using the Vertically and Crosswise Method The base method is great if both numbers are close to the same base, but you’ll encounter many problems in which the numbers aren’t even remotely close to each other.