Question : Directions: Some equations are solved based on certain systems. On the same basis, find the correct answer from amongst the four alternatives for the unsolved equation in the question.
a = 12(390)8; b = 7(134)5; c = 5(?)12
Option 1: 299
Option 2: 289
Option 3: 279
Option 4: 280
Correct Answer: 279
Solution :
Given:
a = 12(390)8; b = 7(134)5; c = 5(?)12
Square the sum of the first and third numbers and then subtract 10 from the resultant, to obtain the middle number –
Here, a = 12(390)8→(12 + 8)
2
– 10 = (20)
2
– 10 = 400 – 10 = 390
b = 7(134)5→(7 + 5)
2
– 10 = (12)
2
– 10 = 144 – 10 = 134
c = 5(?)12→(5 + 12)
2
– 10 = (17)
2
– 10 = 289 – 10 = 279
So, 279 is the required missing term. Hence, the third option is correct.
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