Simplify: 12 + 6 × 3 − 8 ÷ 4
- 26
- 30
- 28 Correct answer.
- 52
Explanation
Under BODMAS, multiplication and division are done before addition and subtraction. Here 6 × 3 = 18 and 8 ÷ 4 = 2, so the expression becomes 12 + 18 − 2 = 28.
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Under BODMAS, multiplication and division are done before addition and subtraction. Here 6 × 3 = 18 and 8 ÷ 4 = 2, so the expression becomes 12 + 18 − 2 = 28.
15% means 15 per hundred, so multiply 240 by 15/100. That gives 3600/100 = 36.
The average equals the sum of the observations divided by their number. The sum is 12 + 18 + 24 + 30 + 36 = 120, and 120 ÷ 5 = 24.
Factorising, 36 = 2² × 3² and 48 = 2⁴ × 3. The highest common factor takes the lowest power of each common prime: 2² × 3 = 12.
Simple interest is P × R × T ÷ 100. Substituting, 5000 × 8 × 3 ÷ 100 = ₹1200.
The total number of parts is 5 + 4 = 9, so each part is worth 720 ÷ 9 = ₹80. The larger share is 5 × 80 = ₹400.
Since 42 × 42 = 1764, the square root of 1764 is 42. Checking neighbours confirms that no other listed value squares to 1764.
Profit is ₹500 − ₹400 = ₹100, and profit percentage is always calculated on the cost price. Thus 100/400 × 100 = 25%.
The amount after 2 years is 8000 × (1.1)² = 8000 × 1.21 = ₹9680. Compound interest is the amount minus the principal, i.e. 9680 − 8000 = ₹1680.
A does 1/12 and B does 1/18 of the work per day, so together they do 1/12 + 1/18 = 5/36 per day. The time taken is the reciprocal, 36/5 = 7.2 days.
Let the speed be x km/h. Then 360/x − 360/(x + 5) = 1, which simplifies to x² + 5x − 1800 = 0. Solving gives x = 40, so the speed is 40 km/h.
From 2πr = 44 with π = 22/7, the radius is 7 cm. The area is πr² = (22/7) × 49 = 154 cm².
Convert the speed to metres per second: 54 × 5/18 = 15 m/s. To pass a pole the train covers its own length, so the time is 150 ÷ 15 = 10 seconds.
By the rule of alligation, the ratio of cheaper to dearer is (40 − 34) : (34 − 30) = 6 : 4 = 3 : 2. Indeed, 3 kg at ₹30 and 2 kg at ₹40 give ₹170 for 5 kg, i.e. ₹34 per kg.
A number is divisible by 9 when its digit sum is a multiple of 9. Here 1 + 2 + 3 + 4 = 10, and the next multiple of 9 is 18, so 8 must be added, giving 1242 whose digit sum is 9.
Subtract 2x from both sides to get x − 7 = 5, then add 7 to both sides to obtain x = 12. Substituting back confirms 29 = 29.
Volume of a cylinder is πr²h. Substituting gives (22/7) × 7 × 7 × 10 = 22 × 7 × 10 = 1540 cm³.
Profit shares are proportional to capital multiplied by time. A's figure is 5000 × 12 = 60000 and B's is 8000 × 6 = 48000, so the ratio is 60000 : 48000 = 5 : 4.
After a 20% discount the customer pays 80% of the price, and after a further 10% discount pays 90% of that, i.e. 0.8 × 0.9 = 0.72 of the marked price. The equivalent single discount is therefore 100% − 72% = 28%.
If the original population is 100, it becomes 110 after the rise and then 110 × 0.9 = 99 after the fall. The net change is a decrease of 1%, because the 10% fall is taken on the larger value.
Net filling per hour is 1/12 + 1/15 − 1/20 = 5/60 + 4/60 − 3/60 = 6/60 = 1/10. The tank therefore fills in 10 hours.
Downstream speed is 10 + 2 = 12 km/h and upstream speed is 10 − 2 = 8 km/h. The times are 24/12 = 2 hours and 24/8 = 3 hours, giving a total of 5 hours.
Squaring both sides gives (x + 1/x)² = x² + 2 + 1/x² = 9. Hence x² + 1/x² = 9 − 2 = 7.
The angles total 180°, and the ratio has 2 + 3 + 4 = 9 parts, so each part is 20°. The angles are 40°, 60° and 80°, of which the largest is 80°.
Adding the three pair rates gives 1/12 + 1/15 + 1/20 = 1/5, so 2(1/A + 1/B + 1/C) = 1/5 and 1/A + 1/B + 1/C = 1/10. Subtracting B and C's combined rate gives 1/A = 1/10 − 1/15 = 1/30, so A alone needs 30 days.
Write each number as a product of prime factors: 36 = 2² × 3² and 84 = 2² × 3 × 7. The HCF is the product of the common prime factors taken with the lowest powers, i.e. 2² × 3 = 12.
The average of a set of numbers is their sum divided by the count of numbers. Here the sum is 4 + 8 + 10 + 14 = 36 and there are 4 numbers, so the average is 36 ÷ 4 = 9.
Simple interest is calculated as SI = (P × R × T) / 100. Substituting P = 5000, R = 8 and T = 3 gives (5000 × 8 × 3) / 100 = ₹1200.
The area of a triangle is half the product of its base and height. So the area is ½ × 12 × 9 = 54 cm².
Expand both squares using the standard identities: (a + b)² = a² + 2ab + b² and (a − b)² = a² − 2ab + b². Subtracting gives 2ab − (−2ab) = 4ab.
For a polygon with n sides, the interior angles add up to (n − 2) × 180°. A hexagon has 6 sides, so the sum is 4 × 180° = 720°.
The decimal 0.75 means 75 hundredths, that is 75/100. Dividing both numerator and denominator by their HCF 25 gives 3/4, which cannot be reduced further.
The median is the middle observation once the data are arranged in order. The values are already in ascending order, and the third of the five values is 9.
Write prime factorisations: 12 = 2² × 3, 15 = 3 × 5 and 20 = 2² × 5. The LCM takes each prime with its highest power, giving 2² × 3 × 5 = 60.
Probability equals favourable outcomes divided by total outcomes. The prime numbers on a die are 2, 3 and 5, giving 3 favourable outcomes out of 6, so the probability is 3/6 = 1/2.
Factorise by finding two numbers whose product is the constant term 6 and whose sum is 5. Those numbers are 2 and 3, so x² − 5x + 6 = (x − 2)(x − 3) and the roots are 2 and 3.
Multiply the two ratios after making the common term b equal: a/c = (a/b) × (b/c) = (3/4) × (8/9) = 24/36 = 2/3. Hence a : c = 2 : 3.
For two years the difference is P × (R/100)². Substituting P = 10000 and R = 10 gives 10000 × (0.1)² = ₹100, which is the interest earned in the second year on the first year's interest.
For the same base, multiplying adds the indices and dividing subtracts them. So the expression equals 2^(3 + 4 − 5) = 2² = 4.
A square of side s has diagonal s√2, so s = 10/√2. The area is s² = (10/√2)² = 100/2 = 50 cm², which is also given directly by the rule area = d²/2.
The curved surface area of a cylinder is 2πrh. Substituting r = 7, h = 5 and π = 22/7 gives 2 × (22/7) × 7 × 5 = 220 cm².
The total of the five numbers is 5 × 27 = 135. Removing 35 leaves 100 to be shared among four numbers, so the new average is 100 ÷ 4 = 25.
From the standard trigonometric table, sin 30° = 1/2 and cos 60° = 1/2. Adding them gives 1/2 + 1/2 = 1.
We need two numbers whose product is +6 and whose sum is −5. The numbers −2 and −3 satisfy both conditions, so the factorisation is (x − 2)(x − 3).
Let the number be N. Then (25/100) × N = 30, so N = 30 × 100/25 = 120.
Take the cost price as ₹100. The marked price is ₹140, and after a 25% discount the selling price is 140 × 0.75 = ₹105, so the profit is ₹5 on ₹100, that is 5%.
Let the numbers be n, n + 2 and n + 4. Their sum is 3n + 6 = 87, so 3n = 81 and n = 27. The largest number is 27 + 4 = 31.
The total work equals 12 × 15 = 180 man-days. To finish the same work in 9 days, the number of men required is 180 ÷ 9 = 20.
The surface area of a sphere is 4πr². Substituting r = 7 and π = 22/7 gives 4 × (22/7) × 49 = 616 cm².
Use the identity x² + y² = (x + y)² − 2xy. Substituting the given values gives 10² − 2 × 21 = 100 − 42 = 58.