The sum of three prime numbers is 90. If one of them exceeds another by 30, then one of the numbers is:
- A67
- B41
- C59
- D47
Solution & Step-by-step Explanation
Let the three prime numbers be p
1
,p
2
, and p
3
.
Given that their sum is 90 (an even number):
p
1
+p
2
+p
3
=90
Since the sum of three numbers is even, either all three numbers must be even, or one must be even and two must be odd.
Since 2 is the only even prime number, one of the primes must be 2. Let p
1
=2.
2+p
2
+p
3
=90⟹p
2
+p
3
=88
We are also given that one prime number exceeds another by 30. Let p
3
−p
2
=30.
Now we have a linear system of equations:
p
3
+p
2
=88
p
3
−p
2
=30
Adding the two equations:
2p
3
=118⟹p
3
=59
Subtracting the equations:
2p
2
=58⟹p
2
=29
Check if 29 and 59 are prime: Yes, both are prime.
Thus, the three prime numbers are 2,29, and 59.
Comparing with the options, 59 is present.
1
,p
2
, and p
3
.
Given that their sum is 90 (an even number):
p
1
+p
2
+p
3
=90
Since the sum of three numbers is even, either all three numbers must be even, or one must be even and two must be odd.
Since 2 is the only even prime number, one of the primes must be 2. Let p
1
=2.
2+p
2
+p
3
=90⟹p
2
+p
3
=88
We are also given that one prime number exceeds another by 30. Let p
3
−p
2
=30.
Now we have a linear system of equations:
p
3
+p
2
=88
p
3
−p
2
=30
Adding the two equations:
2p
3
=118⟹p
3
=59
Subtracting the equations:
2p
2
=58⟹p
2
=29
Check if 29 and 59 are prime: Yes, both are prime.
Thus, the three prime numbers are 2,29, and 59.
Comparing with the options, 59 is present.