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GSEB Solutions for Class 7 Mathematics – Revision 2

GSEB Solutions for Class 7 Mathematics – Revision 2 (English Medium)

GSEB SolutionsMathsScience
Revision 2

Solution 1:

  1. The percentage of Oxygen is 21%.
  2. Percentage of Nitrogen = 78%
    Percentage of Oxygen = 21%
    Hence, there is 57% more Nitrogen than Oxygen.
    (78 – 21)% = 57%
  3. The percentage of other gases is 1%.

Solution 2:

When a number is denoted using the modulus symbol, its absolute value is always positive.

  1. |0| = 0
  2. |10| = 10
  3. |-18| = 18
  4. |-3| = 3
  5. |23| = 23

Solution 3:

  1. (-33) + (-17)
    = -33 – 17
    = -(33 + 17)
    = -50
  2. (-33) – (-17)
    = -33 + 17
    = -16
  3. 0 – 17
    = -17
  4.  (-24) + 24
    = -24 + 24
    = 0
  5.  (-5) + (+5)
    = -5 + 5
    = 5 – 5
    = 0

Solution 4:

  1.  Since 7 is a prime number, it cannot be factorized.
    Hence, multiply 7 by the smallest number 7 to get a perfect square.
    i.e. 7 × 7 = 72 = 49
    √72 = 7
    Thus, 7 should be multiplied by the smallest number 7 to get perfect square 49.
  2.  75
    gseb-solutions-for-class-7-mathematics-revision-2-4.1
    75 = 3 × 5 × 5
    The prime factor 3 does not make a pair.
    Hence, to make the product a perfect square, the number 75 should be multiplied by 3.
    gseb-solutions-for-class-7-mathematics-revision-2-4.2
    Hence, 75 × 3 = 3 × 3 × 5 × 5

Solution 5:

gseb-solutions-for-class-7-mathematics-revision-2-5

Solution 6:

gseb-solutions-for-class-7-mathematics-revision-2-6

Solution 7:

  1.  (a – b + ab) + (b – c + bc) + (c – a + ac)
    = a – b + ab + b – c + bc + c – a + ac
    = a – a – b + b – c + c + ab + bc + ac
    = 0 + 0 + 0 + ab + bc + ac
    = ab + bc + ac
  2. (2lm + 2mn) + (-7lm + 2nl)
    = 2lm + 2mn – 7lm + 2nl
    = 2lm – 7lm + 2mn + 2nl
    = (2 – 7)lm + 2mn + 2nl
    = -5lm + 2mn + 2nl

Solution 8:

  1. (15x3 + 3x2 – 25) – (16x3)
    = 15x3 + 3x2 – 25 – 16x3
    = 15x3 – 16x3 + 3x2 – 25
    = (15 – 16)x3 + 3x2 – 25
    = -x3 + 3x2 – 25
  2.  (m2 + 6mn – 7n2) – (5m2 + 3mn + n2)
    = m2 + 6mn – 7n2 – 5m2 – 3mn – n2
    = m2 – 5m2 + 6mn – 3mn – 7n2 – n2
    = (1 – 5)m2 + (6 – 3)mn + (-7 – 1)n2
    = -4m2 + 3mn – 8n2

Solution 9:

gseb-solutions-for-class-7-mathematics-revision-2-9
∠XPC and ∠PQA are corresponding angles.
∴ m∠XPC = m∠PQA
But m∠PQA = 140° (given)
∴ m∠XPC = 140°

  1.  ∠PQA and ∠DPQ are alternate angles.
    ∴ m∠PQA = m∠DPQ
    But m∠PQA = 14°
    ∴ m∠DPQ = 140°
  2. ∠CPQ and ∠PQA are interior angles on the same side of the transversal.
    (Interior angles on the same side of the transversal are supplementary)
    ∴ m∠CPQ + m∠PQA = 180°
    m∠PQA = 140°
    ∴ 140° + m∠CPQ = 180°
    ∴ m∠CPQ = 180° – 140° = 40°
  3.  ∠BQY and ∠DPQ are corresponding angles.
    ∴ m∠BQY = m∠DPQ
    But m∠DPQ = 140°
    ∴ m∠BQY = 140°
  4.  ∠PQB and ∠DPQ are interior angles on the same side of the transversal.
    ∴ m∠PQB + m∠DPQ = 180°
    But m∠DPQ = 140°
    ∴ m∠PQB + 140° = 180°
    ∴ m∠PQB = 180° – 140° = 40°
  5. ∠XPD and ∠PQB are corresponding angles.
    ∴ m∠XPD = m∠PQB
    But m∠PQB = 40°
    ∴ m∠XPD = 40°
  6.  ∠CPQ and ∠AQY are corresponding angles.
    ∴ m∠CPQ = m∠AQY
    But m∠CPQ = 40°
    ∴ m∠AQY = 40°

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