Are you looking for DAV Maths Solutions for class 8 then you are in right place, we have discussed the solution of the Secondary Mathematics book which is followed in all DAV School. Solutions are given below with proper Explanation please bookmark our website for the further update !! All the Best !!
Unit 4 Brain Teaser | DAV SOLUTIONS CLASS 8 Secondary Mathematics
Q1A. Tick the correct option.
(i) Both x and y are in direct proportion, then 1/x and 1/y are
(a) in direct proportion (b) in inverse proportion
(c) neither indirect nor inverse proportion (d) sometimes indirect and sometimes in inverse proportion
(ii) If two quantities x and y vary inversely with each other, then
(a) x/y remains constant. (b) (x—y) remains constant
(c) (x+ y) remains constant (d) (xy) remains constant
(iii) Both p and q vary directly with each other, When p is 10 and q is 15. which of the following is not a possible pair of corresponding values of p and q?
(a) 15 and 20 (b) 20 and 30 (c) 2 and 3 (d) 5 and 7.5
(iv) If x and y vary directly with each other and x = 24, what is y when constant of variation is 3?
(a) 21 (b) 1/8 (c) 8 (d) 27
(v) Which of the quantities vary inversely with each other?
(a) Distance travelled and cab fare. (b) Area of a land and its cost.
(c) Number of workers and amount of work done. (d) Number of workers and time taken to finish a job.
Q1B. Answer the following questions.
(i) l varies directly as m and l is equal to 5, when m = 2/3. Find l when m = 16/3
(ii) A bowler throws a cricket ball at a speed of 36 km/hr. How long does this ball take to travel a distance of 20 metres to reach the batsman?
(iii) Sweets from a packet were distributed among 50 children and each of them received four sweets. If it is distributed among 40 children, how many sweets will each child get.
(iv) If y is directly proportional to 1/x and x = 2 when y = 20, what is the value of x when y = 1.25?
(v) If l is inversely proportional to √m and l = 6 when m = 4. What is the value of m when l = 4?
2. Determine from the values of x and y given below whether they vary directly, inversely or in neither of these ways
3. If x and y vary inversely and x = 25, when y = 3. Find y, when x = 15.
4. If x and y vary inversely and y = 45. Find x when constant of variation = 9.
5. Oranges cost 27 for 3 dozens in the super market. What is the cost of 8 oranges?
6. A car travels 60 km in 1 hr 30 min. How long will it take to cover a distance of 100 kin at the same speed?
7. The extension of an elastic spring is found to vary directly with the weight suspended from it. If a weight of 75 kg produces an extension of 1.4 cm, calculate the weight that would produce an extension of 9.8 cm?
8. In 25 days, the earth picks up 6 x 10^8 pounds of dust from the atmosphere. How much dust will it pick up in 15 days?
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