Doubtly
@Doubtly · Joined Feb 2021
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- If the cost of bananas is increased by Rs. 10 per dozen, one can get 3 dozen less for Rs.600. Let x be the original cost of 1 dozen bananas , for Rs. 600 we gets y dozens. xy =600 .................... 1 y=600over x By increasing the c... 1
- Find the first two terms of the sequence for which Sn is given below Sn=n^2 (n+1) Answer is 2 , 10 Solution :: To find the first term substitute n=1 in formula S₁=1²(1+1)=1(2)=2 To find the second term, substitute n = 2 in... 1
- Prove. Sec2 A + Cosec2 A = Sec2 A Cosec2 A Proof :: LHS = sec² A + cosec² A =1over(cos²A)+1over(sin²A)=(sin²A+cos²A)over(cos²A sin²A) =1over(cos²A sin²A)=sec²A cosec²A=RHS 1
- Find the area of the sector of a circle of radius 8 cm and arc with length 15 cm. Answer is 60 cm^(2 ) Solution :: Let centre be O red dot radius=OA=8cm=r length of arc= 15cm=L Area of sector= 1over 2× r× l = 1over 2× 8× 1... 1
- Draw a tangent at any point ‘M’ on the circle of radius 3.3 cm and centre ‘O’. Answer :: step-1 } draw circle with radius 3.3 cm , name the centre as "O" and create any point on circle name as "M" . step:2} watch this v... 2
- If a machine is lubricated with oil (a) the mechanical advantage of the machine increases Answer: (c) both its mechanical advantage and efficiency increase Oil reduces friction between the moving parts. Less effort is then wasted... 1
- Refractive index of water with respect to air is 1.33 and that of diamond is 2.42. Refractive index = speed of light in vacuum/speed of light in medium Since the refractive index of diamond is more, hence the speed of light... 1
- Select the correct stability order of the conformation /Rotamers/ Rotational isomers of Ethane Molecule The correct answer is c) Anti-staggered > Skew or Gouche > Partially Eclipsed > Fully Eclipsed EXplaination :: The isomers which can be prod... 1
- Expression for time in terms of G (universal gravitational constant), h (Planck constant) and c (speed of light) is proportional to : The correct option is C) √(Gh/c⁵) Explaination:: F = GM²/R² ⇒ G = [M⁻¹ L³ T⁻²] E = hv ⇒ h = [ML² T⁻¹] C = [LT⁻¹] t ∝ G^x h^y C^z [M⁰ L⁰T¹] =... 1
- According to molecular orbital theory, the species among the following that does not exist is: The correct answer is d) Be₂ According to M.O.T. If bond order of chemical species is zero then that chemical species does not exist Chemica... 1
- In Freundlich adsorption isotherm at moderate pressure, the extent of adsorption (x/m) is directly proportional to Px. The value of x is: The correct answer is d) 1/n Solution : (xover m)=KP^(1over n) x=1over n 1
- In Young’s double-slit experiment, the width of one of the slits is three times the other slit. The correct answer is a) 4:1 Explaination :: A₂=3A₁ Amplitude ∝ width space of space slit I_max = (A₁ + 3A₁)^(2 ) ..............1 and I_min... 1
- Ceric ammonium nitrate and CHCl3/alc. KOH are used for the identification of functional groups The correct answer is option A) Alcohol and amine Solution : Ceric ammonium nitrate and CHCl₃/alc. KOH are used for the identification of fu... 1
- Calgon is used for water treatment. Which of the following statements is NOT true about Calgon? The correct answer is opion A) Calgon contains the 2ⁿd most abundant element by weight in the earth's crust EXplaination :: Order of abundan... 1
- The nature of charge on resulting colloidal particles when FeCl3 is added to excess of hot water is: The correct option is A) positive Explaination :: A positively charged sol of hydrated ferric oxide is formed due to the adsorption of Fe³⁺... 1
- For octahedral Mn(II) and tetrahedral Ni(II) complexes, consider the following statements: The correct answer is b) (I), (II) and (III) only {answer by NTA} Explaination :: 1
- An open beaker of water in quilibrium with water vapour is in a sealed container. When a few grams of glucose Answer: (1) the rate at which water molecules leave the solution decreases At equilibrium, the rate of evaporation (water molecules leaving... 1
- Rate of formation of SO3 in the following reaction 2SO2 + O2 → 2SO3 is 100 g min–1. The correct answer is D) 20 g/min Solution :: dover dt [SO₃]=100 g/min =100over80mole/min =1.25 mole/min -1over2dover dt[SO₂] [SO₃]=-dover d... 1