Class 10 · Maths · Pair of Linear Equations in Two Variables

Substitution method MCQs

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Substitution methodQuiz - Solve & Score

  1. Q1. A fraction becomes 9/11 if 2 is added to numerator and denominator, and 5/6 if 3 is added to both. The fraction is (NCERT):

    • A.3/5
    • B.7/9
    • C.9/11
    • D.5/6

    Answer: B. 7/9

  2. Q2. Solve 7x - 15y = 2 and x + 2y = 3. The value of x is (NCERT):

    • A.3
    • B.29/49
    • C.49/29
    • D.2

    Answer: C. 49/29

    Reading the problem, 7, 15, 2, 2, 3 (math, chapter 'Pair of Linear Equations'). What we must find: the requested quantity. The principle that connects these is - x = 3 - 2y. Substituting and simplifying: x = 3 - 2y → substitute to find x = 49/29. That lands on option C) 49/29. As for the others, option A) '3' fails since Substituting x=3-2y gives x=49/29; option B) '29/49' is wrong because x = 49/29.

  3. Q3. Two numbers are in ratio 5:6; if 8 is subtracted from each, the ratio is 4:5. The numbers are (NCERT):

    • A.35 and 42
    • B.25 and 30
    • C.40 and 48
    • D.50 and 60

    Answer: C. 40 and 48

    Given 5, 6, 8, 4, 5, asked for the unknown. By (5k-8)/(6k-8)=4/5. (5k-8)/(6k-8)=4/5 → k=8. So option C) 40 and 48. Others fail: option A) '35 and 42' doesn't hold - The numbers are 40 and 48; option B) '25 and 30' misses the point - Ratio with -8 gives 4:5 only for 40,48.

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