MATH 210 - Answers

MATH 210 j Fall 2008 j TEST 1 j ANSWERS (18)1a. Write the number 1426 in Egyptian. ( Hint: | | ¨¨¨¨11| Ì ª 1b. Write 1 9 8 4 1 ¨ Ì | ª ) | | | | | as a Roman numeral. M CM LXXX IX 1c. Write the Hindu-Arabic numeral that is equivalent to the Roman numeral M DCC XL VII. 1 1d. 4 7 Write the Hindu-Arabic numeral for the number we state as: “ten trillion, six hundred four million, seventy-three thousand, eight hundred ninety-two” 10,000,000,000,000 +604,000,000 + etc 1e. 7 = 10,000,604,073,892 What is the place value of the 7 in 1,270,968 ? The 7 represents 70,000. It is in the ten-thousands place. 1f. Using each of the digits in 12,407 only once, write the largest number : The largest number using the digits 1&2&4&0&7 each once is 74210 1g. Write the number 6×106 + 3×104 + 5×103 + 7×100 in standard Hindu-Arabic form. That’s 6×1,000,000 + 3×10,000 + 5×1,000 + 7 = 6,035,007 1h. Write the number 4,307 in expanded exponential form. 4000 + 300 + 7 = 1i. 4×1000 + 3×100 + 7×1 = 4×103 + 3×102 + 7×100 Write the number 73,406 in long form (in words, as you would read it). Seventy-three thousand, four hundred six . (15) (6) Notice there is no mention of “and”. 2. State the property illustrated by each statement. Do not use the term “any-order property”. State the full description of the property, including the operation: e.g. “commutative property of addition”. a. x@5 = 5x a. COMMUTATIVE property of MULTIPLICATION b. 78 @99 = 78(100 – 1) = 78@100 – 78@1 b. DISTRIBUTIVE property of MULTIPLICATION over SUBTRACTION c. 72 + (26 + 8) = 72 + (8 + 26) c. COMMUTATIVE property of ADDITION d. 1@ 47,327,676 = 47,327,676 d. IDENTITY property of MULTIPLICATION e. 999@1 = 999 e. IDENTITY property of MULTIPLICATION 3. Name the property that is being illustrated in each example: a. The COMMUTATIVE property of MULTIPLICATION b. The COMMUTATIVE property of ADDITION 4 3x4 0 = /39 3 4 × 3 1 2 3 4 3 0 1 5 6 7 8 9 5 6 7 8 9 4 2 3 4 (4) 4. Give a specific counterexample, using only whole numbers, to show that subtraction is not associative. Your example should fully demonstrate the different results. 15 – (8 – 7) … ( 15 – 8 ) – 7 15 – ( 1 ) … ( 14 (3) )–7 0 5. Draw rectangular arrays illustrating the distributive property for 2×(3+4) = 2×3 + 2×4 = 2 × ( 3 + 4) (3) … 7 + 2×3 2×4 6. For each word problem given, state the interpretation of subtraction illustrated. Possible answers are: Part-Whole (missing addend) Take-away Comparison a. Amazingly, 15 of Ms. Smith’s third-grade class of 27 were on the honor roll last month. How many were not on the honor roll last month? 27 Type of problem: Part-Whole (missing addend) 15 ? b. Joni put a dozen apples on the back porch. Squirrels came in and stole five of the apples. How many are left? M M M M M M Type of problem: Take-away M M M M M M > (2) c. Frank earned 85 on the spelling test, and Ernest earned 60. How much higher is Frank’s score than Ernest’s? Type of problem: Comparison ÆÈÇ ? 7. For each word problem given, state the interpretation of division illustrated. Possible answers are: Partitive Division (PD) Measurement Division (MD) a. 72 eggs is how many dozen? Type of problem: Measurement Division (MD) “How many 12s in 72?” b. We drove 3200 miles across the US in 5 days. What was our average distance per day? Type of problem: Partitive Division (PD) “3200 divided into 5 parts.” (3) 8. This illustration shows measurement division for the problem 23 ÷ 5. Fill in the blanks with appropriate numbers to illustrate the Quotient-Remainder Theorem, as it applies to this division example. 25 = 4 @5 + 3 0 5 10 15 20 23 25 (4) 9. Calculate each of the following divisions. Use the definition of division (“missing factor”) to show why that answer is correct. If the division is undefined, say so, and use the definition of division to explain why. a. 6 ÷ 2 = 3 because: 2 @ 3 = 6 b. 0 ÷ 2 = 0 because: 2 @ 0 = 0 c. 2 ÷ 0 is undefined because: 0 @ ? = 2 has no solution, no answer d. 0 ÷ 0 is undefined because: 0 @ ? = 0 has many solutions, no unique answer; so it is meaningless /19 (12) 10. Illustrate Mental Math techniques to compute the following. Write your answers in a way that shows clearly the manner in which you computed the answer mentally. a. 47 + 78 + 201 + 22 + 53 = 47 + 53 + 78 + 22 + 201 = 100 + 100 + 201 = 301 rearranging, using commutative & associative properties to get these nice compatible combinations b. 847 – 298 +2 +2 = 847 – 298 = 849 – 300 = 549 compensation for subtraction c. 345 + 597 3 = 345 + 597 342 + 600 = = 942 compensation for addition d. 802 × 998 = = = 802 × (1000 – 2) 802000 – 1604 800396 Distributive property (of × over – ) e. 242 × 5 Alternately: = 242 × 10 ÷ 2 = 2420 ÷ 2 = 1210 f. = = = Special relationship between 5, 2 and 10 5 = 10 ÷ 2 So × 5 = × 10 ÷ 2 = 242 ÷ 2 × 10 Special relationship between 5, 2 and 10 Notice the action just reverses the above i.e. ÷ 5 = × 2 ÷ 10 = 242 ÷ 10 × 2 225 ÷ 5 225 × 2 ÷ 10 450 ÷ 10 45 g. 4 × 632 × 25 = (4 × 25) × 632 = 100 × 632 = 63200 (7) rearranging, using commutative & associative properties 11. Use a Chip Model to illustrate fully the subtraction: 304 – 125 . Show the standard arithmetic alongside. HUNDREDS TENS  ONES      /19 —1 2 5 1 7 9 2 3 – 1 1 9 10 14 0 4 2 5 7 9 (6) 12. Determine whether each of the following is true (T) or false (F). (24 ÷ 4) ÷ 2 … 24 ÷ (4 ÷ 2) If false, use a counterexample to demonstrate that it is not true. a. Division is associative. T F ( 6 ) ÷ 2 … 24 ÷ ( 2 ) 3 … 12 FALSE, as demonstrated at right b. For all numbers, ( a + b )2 = a2 + b2 ( 1 + 2 )2 … 1 2 + 22 T F ( )2 … 1 + 4 3 … 9 c. Addition is closed on the set of odd numbers. T 5 F 1 is an odd number, and 3 is an odd number, but 1+3 is 4, not an odd number. So to get the sum of these two odd numbers, we have to go outside the set of odd numbers. (6) 13. When computing 37 × 62 using the standard multiplication algorithm, show what the two lines indicated represent (what are they)? Show the same calculation using the lattice method. Show ALL steps. 6 2 62 1 x37 8 6 3 7 × 62 434 2 1860 30 × 62 2294 4 1 2 4 7 2 9 (5) 4 14. Compute 4362 ÷ 47 using long division. Show an estimation for the first digit of the quotient. (Even if the firs estimate is not correct, one estimate is all you need to show.) Show the correct Quotient and Remainder. 9 2 ² Quotient 47  4 3 6 2 423 132 94 3 8 ² Remainder You can write: 92 R 38 Estimate: 9 50  450 (5) 15. Make a word problem using partitive division for 28÷ 7. Illustrate the complete solution with a bar diagram. 28 Word Problem: ? 28 ÷ 7 = 4 28 toys were divided equally among 7 tots. How many toys did each tot receive? Each tot received 4 toys. (5) 16. Give a full “teacher’s solution”: Jay, Ray and Lee collect stickers. Jay has 3 times as many stickers as Ray. Lee has 50 more than Jay. They have 540 stickers altogether. How many stickers does Ray have? Ray ? Jay 540 Lee 50 540 – 50 490 490 ÷ 7 = 70 Ray has 70 stickers. Check: Ray has 70 Jay has 210 Lee has 260 Total: 490 /27 ² Without Lee’s extra 50, they have 540 – 50 stickers 540 T