TLDR;
This YouTube video by KGS SSC Exams focuses on solving quantitative aptitude questions relevant to the IB Security Assistant exam. The instructor solves previous year's questions, offering detailed explanations and shortcuts. Key topics covered include number systems, compound interest, ratio and proportion, time-speed-distance, profit and loss, averages, and mensuration. The video emphasizes understanding the question types, efficient problem-solving techniques, and time management.
- Focus on previous year's questions for IB Security Assistant exam.
- Covers various topics including number systems, CI, ratio, TSD, profit/loss, averages and mensuration.
- Emphasizes shortcuts and time management.
Question 1: Number System [0:12]
The instructor begins by solving a question related to number systems, specifically focusing on the sum of squares. The question involves the series 1², 2², 3²,... up to 9², with an additional 100 added at the end. The instructor explains the formula for the summation of n² which is n(n+1)(2n+1)/6. By substituting n = 9, the sum of the series up to 9² is calculated as 285. Since the series appears twice, 285 is doubled and then 100 is added, resulting in a final answer of 670.
Question 2: Compound Interest [3:52]
The next question involves compound interest, where ₹64,000 is borrowed at 5% per annum compounded half-yearly for 1.5 years. The instructor breaks down the 1.5 years into three 6-month periods, each with an interest rate of 2.5%. Since 2.5% is equivalent to 1/40, the principal increases by a factor of 41/40 each period. The calculation involves cubing 40 and 41, resulting in ₹64,000 and ₹68,921 respectively. The difference, ₹4,921, represents the interest earned over the 1.5 years.
Question 3: Ratio and Proportion [8:13]
This question involves ratio and proportion with averages. The average weight of three people X, Y, and Z is 50 kg, totaling 150 kg. Given the average weight of X and Y is 44.5 kg, their combined weight is 89 kg. The task is to find the value of (p+q)/r, where p, q, and r are the weights of X, Y, and Z respectively. By subtracting the combined weight of X and Y from the total weight, the weight of Z is found to be 61 kg. Therefore, the expression becomes 89/61, which is approximately 1.46.
Question 4: Time, Speed, and Distance [12:49]
The instructor tackles a time, speed, and distance problem involving two trains traveling between stations A and B, which are 530 km apart. The first train leaves station A at 9:00 AM, and the second leaves station B at 10:00 AM. Both trains travel at 90 km/h. To apply the concept of relative speed, the instructor calculates the distance covered by the first train in the initial hour (90 km). The remaining distance is 440 km. The relative speed is 180 km/h. The time taken to meet is calculated as 2 hours, 26 minutes, and 40 seconds.
Question 5: Profit and Loss [18:15]
This question focuses on profit and loss. The selling price is increased by 40%, which results in the profit percentage increasing from 15% to 40%. The aim is to find the percentage increase in the cost price. Assuming an initial cost price of ₹100, the initial selling price is ₹115. Increasing the selling price by 40% results in a new selling price of ₹161. By testing the options, a 15% increase in the cost price to ₹115 results in a 40% profit margin.
Question 6: Averages [22:53]
The instructor solves a question on averages. Four years ago, the average age of a husband and wife was 25 years. Currently, they have a child, and the average age of the family is 20 years. The current combined age of the husband and wife is 58 years. With the child included, the total age of the family is 60 years. Therefore, the child's age is 2 years.
Question 7: Time, Speed and Distance Formula [24:55]
This question involves the formula d = s1s2 / (s2 - s1) * delta t. A person is 20 minutes late when traveling at 3 km/h and 30 minutes early when traveling at 4 km/h. The difference in time is 50 minutes. Applying the formula, the distance is calculated as 10 km.
Question 8: Ratios [27:57]
The instructor addresses a question on ratios, emphasizing a shortcut. The ratio of boys to girls is given as 16/2 : 15/3, which simplifies to 8:5. The question asks for the original number of girls in the group. Since the number of girls must be a multiple of 5, the answer can be determined directly from the options without further calculation.
Question 9: Profit and Loss [29:44]
A microwave is sold at a 20% loss. If the selling price is increased by ₹2000, there would be a 20% profit. Assuming a cost price of ₹100, the initial selling price is ₹80, and the new selling price is ₹120. The difference of ₹40 corresponds to ₹2000. Therefore, the cost price (100 units) is ₹5000.
Question 10: Time and Work [30:59]
Anu is four times as efficient as Binny. Together, they can complete a task in 12 hours. The combined efficiency is 5 units per hour. The total work is 60 units. If Anu does the work alone, it will take 15 hours.
Question 11: Mensuration [32:36]
The question involves finding the area of a circular track. The circumference of the inner circle is 220, and the circumference of the outer circle is 352. The radius of the inner circle is 35, and the radius of the outer circle is 56. The area of the track is calculated using the formula π(R² - r²), which simplifies to π(R+r)(R-r). The area is 6006.
Question 12: Volume [35:40]
50 solid metal cubes with edges 2 m long and 10 solid cuboids with dimensions 5 m x 4 m x 3 m are melted to form a big cube. The total volume of the cubes is 400, and the total volume of the cuboids is 600. The combined volume is 1000. The side of the new cube is 10.
Question 13: Simple Interest [42:01]
Sharad invests ₹30,000 in two schemes, X and Y, at 10% and 2% interest, respectively. After 2 years, he receives ₹3000 in interest. The interest for 1 year is ₹1500. Using the minimum technique, the instructor calculates the interest earned at 2% on the entire amount, which is ₹600. The remaining interest of ₹900 is due to the additional 8% on scheme X. Solving for X, the amount invested in scheme X is ₹11,250.
Question 14: Averages - Replacement [45:22]
In a group of eight people, the average weight increases by 5/2 kg when a person weighing 50 kg is replaced. The increase in total weight is 20 kg. Therefore, the weight of the new person is 70 kg.
Question 15: Discount and VAT [47:01]
A shopkeeper offers a 20% discount on goods marked at ₹2000, followed by a 15% VAT. The discounted price is ₹1600. Adding 15% VAT results in a final price of ₹1840.
Class Information [49:18]
The instructor provides information about upcoming classes. There will be a marathon session from 1:00 PM to 3:00 PM on Saturday, featuring both previous year's questions and practice questions. Regular classes from Monday onwards will be held from 1:30 PM to 2:30 PM, focusing on previous year's questions and analysis.