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15 mins SSC Maths Set

15 mins SSC Maths Set 23 Solution

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1. Question / प्रश्न

If α and β are roots of x² − 11x + 24 = 0, find α² + β².
यदि α तथा β, x² − 11x + 24 = 0 के मूल हैं, तो α² + β² ज्ञात कीजिए।

Answer / उत्तर: 73

Solution / हल:
For x² − 11x + 24 = 0,

α + β = 11
αβ = 24

α² + β² = (α + β)² − 2αβ

= 11² − 2 × 24

= 121 − 48

= 73


2. Question / प्रश्न

If one root of x² − kx + 12 = 0 is twice the other, find k.
यदि x² − kx + 12 = 0 का एक मूल दूसरे का दोगुना है, तो k ज्ञात कीजिए।

Answer / उत्तर: 6√2

Solution / हल:
Let roots be x and 2x.

Product of roots = 12

x × 2x = 12

2x² = 12

x² = 6

x = √6

Sum of roots = k

k = x + 2x = 3x

k = 3√6

Now, 3√6 = 6√2

So, k = 6√2


3. Question / प्रश्न

The number of factors of 3600 which are perfect squares is:
3600 के पूर्ण वर्ग भाजकों की संख्या ज्ञात कीजिए।

Answer / उत्तर: 12

Solution / हल:
3600 = 36 × 100

= 2⁴ × 3² × 5²

For perfect square factors, powers must be even.

For 2⁴: powers 0, 2, 4 → 3 choices

For 3²: powers 0, 2 → 2 choices

For 5²: powers 0, 2 → 2 choices

Total perfect square factors = 3 × 2 × 2 = 12

Note: Given options do not contain 12.


4. Question / प्रश्न

Find the remainder when 3¹⁰⁰ is divided by 7.
3¹⁰⁰ को 7 से भाग देने पर शेषफल ज्ञात कीजिए।

Answer / उत्तर: 4

Solution / हल:
Powers of 3 modulo 7:

3¹ = 3

3² = 9 ≡ 2

3³ = 6

3⁴ = 18 ≡ 4

3⁵ = 12 ≡ 5

3⁶ = 15 ≡ 1

Cycle length = 6

100 ÷ 6 leaves remainder 4

So, 3¹⁰⁰ has same remainder as 3⁴.

3⁴ = 81

81 ÷ 7 gives remainder 4


5. Question / प्रश्न

If tan θ = 3/4, then sec θ − cos θ equals:
यदि tan θ = 3/4 है, तो sec θ − cos θ का मान ज्ञात कीजिए।

Answer / उत्तर: 9/20

Solution / हल:
tan θ = 3/4

Using 3-4-5 triangle:

sin θ = 3/5
cos θ = 4/5
sec θ = 5/4

sec θ − cos θ = 5/4 − 4/5

= (25 − 16)/20

= 9/20


6. Question / प्रश्न

If sin θ + cos θ = √2, then θ equals:
यदि sin θ + cos θ = √2 है, तो θ का मान क्या होगा?

Answer / उत्तर: 45°

Solution / हल:
At θ = 45°:

sin 45° = 1/√2

cos 45° = 1/√2

sin 45° + cos 45° = 1/√2 + 1/√2

= 2/√2

= √2

So, θ = 45°


7. Question / प्रश्न

In a triangle, sides are 13 cm, 14 cm and 15 cm. Find its area.
एक त्रिभुज की भुजाएँ 13 सेमी, 14 सेमी तथा 15 सेमी हैं। उसका क्षेत्रफल ज्ञात कीजिए।

Answer / उत्तर: 84 cm²

Solution / हल:
Using Heron’s formula:

s = (13 + 14 + 15)/2

s = 42/2 = 21

Area = √[s(s − a)(s − b)(s − c)]

= √[21(21 − 13)(21 − 14)(21 − 15)]

= √[21 × 8 × 7 × 6]

= √7056

= 84 cm²


8. Question / प्रश्न

A tangent touches a circle at P. Radius OP = 10 cm. Length of tangent from a point 26 cm away from O is:
एक स्पर्श रेखा वृत्त को P पर स्पर्श करती है। OP = 10 सेमी है। O से 26 सेमी दूर स्थित बिंदु से खींची गई स्पर्श रेखा की लंबाई ज्ञात कीजिए।

Answer / उत्तर: 24 cm

Solution / हल:
Radius and tangent are perpendicular.

So, triangle is right-angled.

Distance from centre to external point = 26 cm

Radius = 10 cm

Tangent length = √(26² − 10²)

= √(676 − 100)

= √576

= 24 cm


9. Question / प्रश्न

Distance between points (3,4) and (15,9) is:
(3,4) तथा (15,9) के बीच की दूरी ज्ञात कीजिए।

Answer / उत्तर: 13

Solution / हल:
Distance = √[(15 − 3)² + (9 − 4)²]

= √[12² + 5²]

= √(144 + 25)

= √169

= 13


10. Question / प्रश्न

The area of triangle formed by (0,0), (8,0) and (3,6) is:
(0,0), (8,0) तथा (3,6) से बने त्रिभुज का क्षेत्रफल ज्ञात कीजिए।

Answer / उत्तर: 24

Solution / हल:
Base = 8 units

Height = 6 units

Area = 1/2 × Base × Height

= 1/2 × 8 × 6

= 24


11. Question / प्रश्न

A train 180 m long crosses a pole in 9 seconds. Find its speed.
180 मीटर लंबी ट्रेन 9 सेकंड में एक खंभे को पार करती है। उसकी गति ज्ञात कीजिए।

Answer / उत्तर: 72 km/h

Solution / हल:
Speed = Distance / Time

= 180 / 9

= 20 m/s

Convert into km/h:

20 × 18/5 = 72 km/h


12. Question / प्रश्न

A boat goes 30 km downstream in 2 hours and upstream in 3 hours. Speed of stream:
एक नाव 30 किमी धारा के साथ 2 घंटे में तथा धारा के विरुद्ध 3 घंटे में तय करती है। धारा की गति ज्ञात कीजिए।

Answer / उत्तर: 2.5 km/h

Solution / हल:
Downstream speed = 30/2 = 15 km/h

Upstream speed = 30/3 = 10 km/h

Speed of stream = (Downstream speed − Upstream speed)/2

= (15 − 10)/2

= 2.5 km/h


13. Question / प्रश्न

A can do a work in 24 days and B in 36 days. Working together, they complete it in:
A एक कार्य को 24 दिनों में तथा B 36 दिनों में पूरा करता है। दोनों मिलकर कार्य कितने दिनों में पूरा करेंगे?

Answer / उत्तर: 14.4 days

Solution / हल:
A’s 1 day work = 1/24

B’s 1 day work = 1/36

Together work = 1/24 + 1/36

LCM = 72

= 3/72 + 2/72

= 5/72

Time = 72/5

= 14.4 days


14. Question / प्रश्न

A vessel contains milk and water in ratio 7:5. If 12 litres water is added, ratio becomes 7:8. Find original quantity.
एक बर्तन में दूध और पानी का अनुपात 7:5 है। यदि 12 लीटर पानी मिलाया जाए तो अनुपात 7:8 हो जाता है। प्रारंभिक मात्रा ज्ञात कीजिए।

Answer / उत्तर: 48 litres

Solution / हल:
Let milk = 7x and water = 5x.

After adding 12 litres water:

Milk : Water = 7x : (5x + 12)

Given ratio = 7 : 8

7x/(5x + 12) = 7/8

8x = 5x + 12

3x = 12

x = 4

Original quantity = 7x + 5x = 12x

= 12 × 4

= 48 litres


15. Question / प्रश्न

A shopkeeper marks an article 50% above cost price and gives 20% discount. Profit percentage is:
एक दुकानदार वस्तु का अंकित मूल्य क्रय मूल्य से 50% अधिक रखता है तथा 20% छूट देता है। लाभ प्रतिशत ज्ञात कीजिए।

Answer / उत्तर: 20%

Solution / हल:
Let CP = ₹100

Marked Price = ₹150

After 20% discount:

SP = 150 × 80/100

= ₹120

Profit = 120 − 100 = ₹20

Profit% = 20%


16. Question / प्रश्न

In how many ways can a committee of 3 be formed from 8 persons?
8 व्यक्तियों में से 3 सदस्यीय समिति कितने तरीकों से बनाई जा सकती है?

Answer / उत्तर: 56

Solution / हल:
Number of ways = ⁸C₃

= 8 × 7 × 6 / 3 × 2 × 1

= 336 / 6

= 56


17. Question / प्रश्न

Number of arrangements of the word 'SUCCESS' is:
'SUCCESS' शब्द के भिन्न व्यवस्थापनों की संख्या ज्ञात कीजिए।

Answer / उत्तर: 420

Solution / हल:
Word SUCCESS has 7 letters.

Repeated letters:

S = 3 times

C = 2 times

Total arrangements = 7! / (3! × 2!)

= 5040 / (6 × 2)

= 5040 / 12

= 420


18. Question / प्रश्न

Two dice are thrown. Probability of getting sum equal to 8:
दो पासे फेंके जाते हैं। योग 8 आने की प्रायिकता ज्ञात कीजिए।

Answer / उत्तर: 5/36

Solution / हल:
Total outcomes = 36

Sum 8 outcomes:

(2,6), (3,5), (4,4), (5,3), (6,2)

Favourable outcomes = 5

Probability = 5/36


19. Question / प्रश्न

A bag contains 4 red and 6 blue balls. Probability of drawing a red ball:
एक थैले में 4 लाल तथा 6 नीली गेंदें हैं। लाल गेंद निकलने की प्रायिकता ज्ञात कीजिए।

Answer / उत्तर: 2/5

Solution / हल:
Red balls = 4

Blue balls = 6

Total balls = 10

Probability of red ball = 4/10

= 2/5


20. Question / प्रश्न

A cube of side 10 cm is painted and cut into 1000 equal cubes. Number of cubes with exactly one face painted:
10 सेमी भुजा वाले घन को रंगकर 1000 समान छोटे घनों में काटा गया। ठीक एक सतह रंगे हुए घनों की संख्या ज्ञात कीजिए।

Answer / उत्तर: 384

Solution / हल:
1000 = 10 × 10 × 10

So, cube is cut into 10 parts along each edge.

Number of small cubes with exactly one face painted:

= 6(n − 2)²

= 6(10 − 2)²

= 6 × 8²

= 6 × 64

= 384


21. Question / प्रश्न

Volume ratio of two spheres whose radii are in ratio 3:5:
दो गोलों की त्रिज्याओं का अनुपात 3:5 है। उनके आयतनों का अनुपात ज्ञात कीजिए।

Answer / उत्तर: 27:125

Solution / हल:
Volume of sphere is proportional to r³.

Radius ratio = 3:5

Volume ratio = 3³ : 5³

= 27 : 125


22. Question / प्रश्न

If x + 1/x = 5, then x² + 1/x² equals:
यदि x + 1/x = 5 है, तो x² + 1/x² ज्ञात कीजिए।

Answer / उत्तर: 23

Solution / हल:
Given:

x + 1/x = 5

Squaring both sides:

(x + 1/x)² = 25

x² + 1/x² + 2 = 25

x² + 1/x² = 25 − 2

= 23


23. Question / प्रश्न

If roots of x² − 12x + k = 0 differ by 4, then k equals:
यदि x² − 12x + k = 0 के मूलों का अंतर 4 है, तो k ज्ञात कीजिए।

Answer / उत्तर: 32

Solution / हल:
Let roots be α and β.

α + β = 12

αβ = k

Given:

α − β = 4

Using identity:

(α − β)² = (α + β)² − 4αβ

4² = 12² − 4k

16 = 144 − 4k

4k = 128

k = 32


24. Question / प्रश्न

The smaller angle between the hands of a clock at 4:20 is:
4:20 बजे घड़ी की सुइयों के बीच छोटा कोण ज्ञात कीजिए।

Answer / उत्तर: 10°

Solution / हल:
At 4:20,

Minute hand angle = 20 × 6 = 120°

Hour hand angle = 4 × 30 + 20 × 0.5

= 120 + 10

= 130°

Difference = 130 − 120

= 10°


25. Question / प्रश्न

A sum of money becomes ₹13,310 in 3 years at 10% compound interest per annum. Find the principal.
एक राशि 10% वार्षिक चक्रवृद्धि ब्याज की दर से 3 वर्षों में ₹13,310 हो जाती है। मूलधन ज्ञात कीजिए।

Answer / उत्तर: ₹10,000

Solution / हल:
Amount = ₹13,310

Rate = 10% per annum

Time = 3 years

Formula:

Amount = Principal × (1 + R/100)³

13310 = P × (1 + 10/100)³

13310 = P × (11/10)³

13310 = P × 1331/1000

P = 13310 × 1000 / 1331

P = ₹10,000

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