Practice · check as you go
Lesson 3 practice: Changes in a row, and points
Five questions: four on lesson 3 and one from lesson 2. Every wrong option names the mistake it comes from.
Pick an option and press “Check”: the right answer and why show at once. Your score comes at the end, and the clock only counts the time you take.
- Right answer +1. A wrong answer costs nothing.
- Questions come in Hindi and English. Switch any question with “Language”; questions in English only cannot switch.
- Pass mark: 3.
Untimed. +1 for each right answer, no negative marks. After each answer you see why it is right or wrong.
Sample questions with solutions
A few questions like the ones in this test, with the right answer and why.
- Question 1A college has 450 students, and 18% of them come by bus. How many students come by bus?
- 25
- 81Right answer
- 369
- 810
Explanation1% of 450 = 4.5, so 18% = 18 × 4.5 = 81 students.
Check: 10% of 450 = 45 and 8% of 450 = 36, so 45 + 36 = 81. - Question 2In a 75-question mock test, Arjun answered 57 questions correctly. What percent of the questions did he answer correctly?
- 24%
- 7.6%
- 76%Right answer
- 18%
Explanation1% of 75 = 0.75, and 57 ÷ 0.75 = 76. So he answered 76% correctly.
Check: 76% of 75 = 57. - Question 3In a ward election, 2,340 people voted. This was 65% of the registered voters. How many voters are registered?
- 1,521
- 3,600Right answer
- 3,861
- 36
Explanation65% is 2,340, so 1% = 2,340 ÷ 65 = 36, and 100% = 36 × 100 = 3,600 voters.
Check: 65% of 3,600 = 2,340. - Question 4Rakesh earns ₹24,000 a month. He pays 40% of it as rent, and then spends 25% of the remaining money on travel. How much money is left?
- ₹8,400
- ₹13,200
- ₹10,800Right answer
- ₹3,600
ExplanationRent: 40% of 24,000 = 9,600, leaving 24,000 − 9,600 = 14,400.
Travel: 25% of 14,400 = 3,600, leaving 14,400 − 3,600 = 10,800.
Check: he keeps 75% of 60% of his pay, and 75% of 60% = 45%, and 45% of 24,000 = 10,800. - Question 5In a school of 1,500 students, 60% are girls. 30% of the girls and 20% of the boys walk to school. What percent of all the students walk to school?
- 50%
- 25%
- 26%Right answer
- 18%
ExplanationGirls: 60% of 1,500 = 900, and 30% of 900 = 270 walk. Boys: 1,500 − 900 = 600, and 20% of 600 = 120 walk.
Walkers: 270 + 120 = 390, and 390 ÷ 1,500 × 100 = 26%.
Shortcut: 60% of 30% + 40% of 20% = 18% + 8% = 26%.