Exam 11: Number Theory

arrow
  • Select Tags
search iconSearch Question
  • Select Tags

When you were a spy, two of your paid informants gave you the following information about the same secret code number: Informant 1: "The code number is 33 × 70 × some odd number." Informant 2: "The code number is 35 × 66 × some even number." What can you tell from your informants' information?

Free
(Essay)
4.8/5
(30)
Correct Answer:
Verified

Their information is inconsistent. Although the given factors (33 × 70 and 35 × 66) do give the same prime factorizations, informant 2's "even number" would involve another factor of 2 that informant 1's odd number could not.

Is the following sentence true? If it is, explain why. If it is not, give a counterexample. If a number has n factors (n > 1), then the square of the number has 2n factors.

Free
(Essay)
4.9/5
(35)
Correct Answer:
Verified

No, this is not true. Students should have no trouble finding a counterexample. (The question is just testing the ability to read an if-then statement and of knowing what a counterexample is.)

Is it possible to find a nonzero whole number m so that 14m = 260 × 759? Explain.

Free
(Essay)
4.8/5
(29)
Correct Answer:
Verified

No. Since 14 = 2 × 7, 14 to any power will have the same number of twos as sevens.

Note: This is a theory question. Do not use a calculator for this question. Is it possible, for some choice of positive whole numbers m and n, that 35m = 25n? Justify your answer.

(Essay)
4.8/5
(30)

The following sounds all right, but it is not always true. Give a counterexample. Suppose that k is NOT a factor of m, and k is NOT a factor of n. Then k is NOT a factor of m + n.

(Essay)
4.8/5
(37)

Write these numbers in simplest form. A) 2665\frac { 26 } { 65 } B) 616792\frac { 616 } { 792 } C) 129215\frac { 129 } { 215 }

(Short Answer)
4.7/5
(28)

Which numbers below divide into 11,220? 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20

(Short Answer)
4.8/5
(39)

Note: This is a knowledge of number theory question. Do not use a calculator for this question. Select each of the given choices that is a factor of the given number n. n = 22 . 103 . 711 . 135  Choices: 814212835\text { Choices: } 8 \quad 14 \quad 21 \quad 28 \quad 35

(Short Answer)
4.8/5
(37)

State a divisibility test for 4, and explain why it works.

(Essay)
4.8/5
(27)

Which numbers are prime? If a number is not prime, list at least three factors following the number. 3 5,231,211 61\cdot73 121 43

(Essay)
4.9/5
(32)

Is there a whole number M that would make this true? If so, tell what M is. If not, tell why not. A) 35 . 52 . 173 = 34 . 174 . M B) 24 . 72 . 118 . 22 = 25 . 7 . 116 . M

(Essay)
4.8/5
(37)

Two football players are working out by running around a track. The first can run the track in 3 minutes, and the second one can run the track in 4 minutes. If they begin at the starting point at the same time and run in the same direction at the same rates, when will they both be at the starting point again?

(Short Answer)
4.9/5
(31)

Consider this equation: 3,721,164 = 12 × 172 × 29 × 37 Give the prime factorization of 372,116,400 (notice the extra two zeros). Hint: Do not work too hard.

(Essay)
4.9/5
(29)

A) State a divisibility test for 8. B) Explain why your test in A will definitely work, using the general seven-digit number, abcdefg, in your explanation.

(Essay)
4.9/5
(34)

Name the number of factors of each of these numbers and list them, in factored form. A) 52 × 173 B) 35

(Essay)
4.8/5
(29)

When the number 540 is written as a product of its prime factors in the form a2b3ca ^ { 2 } b ^ { 3 } c , what is the numerical value of a + b + c? Choose one of the following:

(Multiple Choice)
4.8/5
(29)

Note: This is a knowledge of number theory question. Do not use a calculator for this question. Select any choice that is a factor of 80,000,000,005,332. 3 4 5 6 8 9 12 15

(Short Answer)
4.8/5
(43)

Write the prime factorization of the following. (Show your work.) A) 1485 B) 792 C) Name all common factors of 1485 and 792. (They can be in factored form.) D) What is the greatest common prime factor of 1485 and 792?

(Short Answer)
4.8/5
(34)

Of what numbers, if any, is zero a multiple? Explain your answer.

(Short Answer)
4.9/5
(32)

If n = 43,759,462,138,999,999,249 + 76,432,1572, then is n an even number or an odd number? Explain your answer.

(Essay)
4.8/5
(38)
Showing 1 - 20 of 57
close modal

Filters

  • Essay(0)
  • Multiple Choice(0)
  • Short Answer(0)
  • True False(0)
  • Matching(0)