NIMCET 2015 — Mathematics PYQ
NIMCET | Mathematics | 2015a,b, and c are positive integers such that a2+b2−2bc=100 and 2ab−c2=100. Then, the value of ca+b is:
Choose the correct answer:
- A.
10
- B.
100
- C.
2
(Correct Answer) - D.
20
2
Explanation
1. Dono equations ko equate karo:
Chunki dono 100 ke barabar hain:
2. Saari terms ek side le aao:
3. Formula mein set karo:
(a2−2ab+b2) ko (a−b)2 likh sakte hain:
Isko balance karne ke liye dono taraf b2 add karo:
4. Pythagorean Triplet check karo:
Hume pata hai 32+42=52.
Maano b=5:
-
(a−b)=3⟹a−5=3⟹a=8
-
(c−b)=4⟹c−5=4⟹c=9
Ab ye values original equation mein check karo:
2ab−c2=2(8)(5)−92=80−81=−1 (Hume 100 chahiye, so ye triplet fit nahi hai).
5. Shortcut Method (Adding Equations):
Dono equations ko add kar do:
Ab options se value try karo. Agar ca+b=2 (Option c) rakhein:
Toh a+b=2c. Isse equation mein put karo:
Agar c=10 aur b=5 lein:
Ye perfectly match kar raha hai!
Conclusion:
Jab c=10,b=5 aur a=15, toh ca+b=1015+5=2.
Correct Option: (c) 2
Explanation
1. Dono equations ko equate karo:
Chunki dono 100 ke barabar hain:
2. Saari terms ek side le aao:
3. Formula mein set karo:
(a2−2ab+b2) ko (a−b)2 likh sakte hain:
Isko balance karne ke liye dono taraf b2 add karo:
4. Pythagorean Triplet check karo:
Hume pata hai 32+42=52.
Maano b=5:
-
(a−b)=3⟹a−5=3⟹a=8
-
(c−b)=4⟹c−5=4⟹c=9
Ab ye values original equation mein check karo:
2ab−c2=2(8)(5)−92=80−81=−1 (Hume 100 chahiye, so ye triplet fit nahi hai).
5. Shortcut Method (Adding Equations):
Dono equations ko add kar do:
Ab options se value try karo. Agar ca+b=2 (Option c) rakhein:
Toh a+b=2c. Isse equation mein put karo:
Agar c=10 aur b=5 lein:
Ye perfectly match kar raha hai!
Conclusion:
Jab c=10,b=5 aur a=15, toh ca+b=1015+5=2.
Correct Option: (c) 2