ORAL DRILL 1. Find from the above table the sum to which $1 will amount in ten years at 4 %. 2. To what will $1 amount in seven years at 6% ? 7. To what will $10 amount in 10 years at 7 %? 8. To what will $100 amount in 7 years at 6% ? 9. To what will $1000 amount in 12 years at 7% ? 10. To what will $1000 amount in 20 years at 5%? ORAL DRILL 1. Find from the table the square of 18. 2. Obtain from the table the square root of 12. 3. What is the cube root of 12? 4. What is the square of 16? 5. What is the square of 17? 6. What is the cube of 18? 7. What is the circumference of a circle whose diameter is 3? 8. What is the area of a circle whose diameter is 14? 9. What is the circumference of a circle whose diameter is 15? 10. What is the area of a circle whose diameter is 20? CHAPTER VIII SQUARE ROOT AND CUBE ROOT Square Root The square root of a number is one of the two equal numbers which multiplied together will produce the number. Thus, 7 is the square root of 49, and is the square root of The square root of a number is usually indicated by writing the number under the radical sign. The expression 81 is read "the square root of 81.” The square root of a fraction is found by taking the square root of the numerator and of the denominator. Thus, the square root of is . 16 = Since 112, 100=102, 10,000 1002, and so on, the square root of a number between 1 and 100 lies between 1 and 10; of a number between 100 and 10,000, lies between 10 and 100. In other words, the square root of a number expressed by one or two figures is a number of one figure; of a number expressed by three or four figures is a number of two figures; and so on. If therefore a number is divided into groups of two figures each, from right to left, the number of figures in its square root will be equal to the number of groups of figures. The last group to the left may consist of one figure or of two figures. ORAL DRILL What are the square roots of the following numbers? Since 625 consists of two groups of figures, its square root is composed of two figures, tens and units. Since the square of tens is hundreds, 6 hundreds must be the square of at least 2 tens. Two of D is small, if 225 is divided by 40, the combined length of B and C, the quotient will indicate the approximate width of these additions. The quotient is 5; the entire length of B, C, and D is 20+20 + Rule. (1) Beginning at the units' place, separate the number into groups of two figures each. (2) Find the largest square in the first group on the left and write its square root as the first figure in the answer. (3) Subtract its square from the group and annex the second group to the remainder. (4) For a trial divisor use twice the part of the root already found. Divide the remainder, omitting the last figure, by this trial divisor, and annex the quotient to the root and also to the trial divisor. (5) Multiply the complete divisor by the second figure of the root and subtract the product from the remainder. (6) Double the part of the root already found, for another trial divisor, and proceed as before. (7) Continue this process until all of the groups have been used. NOTE. - When a zero occurs in the root, annex a zero to the trial divisor, bring down another group, and proceed as before. |