Advertisements
Advertisements
प्रश्न
If 3 is the least prime factor of number a and 7 is the least prime factor of number b, then the least prime factor of a + b, is
विकल्प
2
3
5
10
उत्तर
Since `7+3=10`
The least prime factor of a+b has to be 2; unless a +b is a prime number greater than 2.
Suppose a +b is a prime number greater than 2. Then a+b must be an odd number
o one of a or b must be an even number.
Suppose then that a is even. Then the least prime factor of a is 2; which is not 3 or 7. So a can not be an even number nor can b be an even number. Hence a+b can not be a prime number greater than 2 if the least prime factor of a is 3 and b is 7.
Thus the answer is 2.
Hence the correct choice is (a).
APPEARS IN
संबंधित प्रश्न
Find the largest number which exactly divides 280 and 1245 leaving remainders 4 and 3, respectively.
Show that every positive even integer is of the form 4m and that every positive odd integer is of the form 4m + 1 for some integer m.
Using prime factorization, find the HCF and LCM of 8, 9, 25 .
Find the greatest number of four digits which is exactly divisible by 15, 24 and 36.
Find the least number of square tiles required to pave the ceiling of a room 15m 17cm long and 9m 2cm broad.
Show that \[2 - \sqrt{3}\] is an irrational number.
Prove that \[2\sqrt{3} - 1\] is an irrational number.
The decimal expansion of the rational number \[\frac{14587}{1250}\] will terminate after
There are 312, 260 and 156 students in class X, XI and XII respectively. Buses are to be hired to take these students to a picnic. Find the maximum number of students who can sit in a bus if each bus takes equal number of students ______.
Assertion: If the HCF of 510 and 92 is 2, then the LCM of 510 and 92 is 32460.
Reason: As HCF (a, b) × LCM (a, b) = a × b
