Questions asked by Enoch YU

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• A tablet contains the same number of moles of CaCO3 and MgCO3. One tablet reacted with excess hydrochloric acid to produce 0.44g of Carbon Dioxide. CaCO3 + 2HCl = CaCl2 + CO2 + H2O MgCO3 + 2HCl = MgCl2 + CO2 + H2O How many moles of CaCO3 are in a tablet?
  
• SO2 + Cl2 = SO2Cl2 If 8g of SO2 is mixed with 14.2g of Cl2, and one mole of SO2Cl2 is 135g, What is the number of moles in Cl2 (chlorine) and SO2 (sulfur dioxide)?
  
• A tablet contains CaCO3 and reacted with excess hydrochloric acid to produce 0.44g of Carbon Dioxide. CaCO3 + 2HCl = CaCl2 + CO2 + H2O MgCO3 + 2HCl = MgCl2 + CO2 + H2O How many moles of CaCO3 are in a tablet?
  
• What is #1/1 + 1/(1+2) + 1/(1+2+3) + ....... + 1/(1+2+3 ...... +2015)# ?
  
• The diagram shows a triangle ABC where AB = AC, BC = AD and Angle BAC = 20 Degrees. What is Angle ADB?
  
• If #a + b + c = 2015# and #1/(a+b) + 1/(b+c) + 1/(c+a) = 1/65#, what is #c/(a+b) + b/(c+a) + a/(b+c)# ?
  
• Ali has 6 books, while Adam has 7 books. How many possible ways can they exchange 4 books with each other?
  
• What is the remainder of 333^444 + 444^333 divided by 7?
  
• What is the value of (2+root5)^1/3 + (2-root5)^1/3 ?
  
• What is it simplified? Thanks for the answer.
  
• What is the value of sin(10)cos(20)sin(30)cos(40)sin(50)cos(60)sin(70)cos(80)? Not in radians, in degrees.
  
• What is the value of it? Thank you in advance.
  
• What is PC? Please explain how did you work it out.
  
• What is the value of f(1) + f(2) + f(3) + ...... f(10)? Thanks in advance for the answer.
  
• What is the minimum value? Thanks in advance.
  
• What is the area enclosed? Please explain how. Thanks in advance
  
• What is the following simplified? Thanks in advance for the answer.
  
• What is the value of tan(9) - tan(27) - tan(63) + tan(81)? (all in degrees)
  
• What is the area of the smaller square? Please tell how. Thanks in advance.
  
• What is the sum of all three digit numbers (abc) such that (ab) * (cc) * (abc)=(abcabc)? (each letter represents one digit of the three digit number)
  
• A train has a speed of 5m/s while a bird has a speed of 10m/s. It takes 80 secs for the bird to fly from the back of the train to the front, and back again. How long is the train?
  
• Let (abcd) be a four digit number (each letter represents one digit). If (abcd)+(abc)+(ab)+(a) = 2018, what is the product of a*b*c*d?
  
• How many numbers of (abc), where each letter represents a digit, that (2018abc) is divisible by 3, 7, 13?
  
• How many positive integer solutions are there to the following? This is from a non-calculator test.
  
• If ab + bc + ca is equal or greater than 2, what is the minimum possible value for a^2 + b^2 + c^2? This was on a noncalculator paper
  
• Starting at 12, on a 12 hour clock, how many times does the hour hand be perpendicular to the minute hand over a 12 hour period? Is there any mathematical method to solve it apart from counting?