Reason + multiplication - math problems

Number of problems found: 81

  • The manufacturer
    cd_disc The manufacturer found that 3% of the plates produced had a malfunction. Of the compliant, 75% are first and 25% second. What is the probability of producing first and second class plates?
  • Boys and girls
    dancers There are 20 boys and 10 girls in the class. How many different dance pairs can we make of them?
  • Divide
    hrusky How many different ways can three people divide 7 pears and 5 apples?
  • Eggs
    egg_2 3400 eggs sliced hens for February and March. We have to calculate how many hens can make 3400 eggs when one hen give 2 eggs a day for 59 days.
  • Dinning room
    cukriky_14 How many different combinations can we choose if there are 3 soups, 5 kinds of main dish and 2 desserts in the dining room?
  • Holidays with grandmam
    saty We have packed three T-shirts - white, red, orange and five pants - blue, green, black, pink and yellow. How many days can we spend with the old mother if we put on a different combination of clothes every day?
  • Bookshelf and books
    bookshelf How many ways can we place 7 books in a bookshelf?
  • Pages counting
    books_39 There are pages numbered from 2 to 104 in the book. How many digits have to be printed to number the pages?
  • Symbols
    my If 2*3 = 60 ; 3*4 = 120 and 4*5 = 200, what is 2*5?
  • Warmer weather
    teplomer_1 This morning it was -6 °C. What temperature did the thermometer show yesterday if it was three times warmer?
  • Progression
    sequence_geo_10 -12, 60, -300,1500 need next 2 numbers of pattern
  • Associative law multiplication
    sale_4 In a warehouse, you obtain a 20% discount but you must pay a 15% sales tax. Which would you prefer to have calculated first: discount or tax? Explain. (result write as: 1 = first discount, 2 = first tax, 3 = no matter what first)
  • Unknown number 16
    numbers_35 My number's tens is three times more then ones My number's ones is twice the number of thousands and my number's hundreds is half the number of of tens. I have two ones. which number am I?
  • Odd/even number
    numbers2_49 Pick any number. If that number is even, divide it by 2. If it's odd, multiply it by 3 and add 1. Now repeat the process with your new number. If you keep going, you'll eventually end up at 1. Every time. Prove. ..
  • Z7-I-4 stars 4949
    hviezdicky_mo Write instead of stars digits so the next write of product of the two numbers to be valid: ∗ ∗ ∗ · ∗ ∗ ∗ ∗ ∗ ∗ ∗ 4 9 4 9 ∗ ∗ ∗ ∗ ∗ ∗ 4 ∗ ∗
  • MO Z6-6-1
    kruhy_1 Write integers greater than 1 to the blanks in the following figure, so that each darker box was product of the numbers in the neighboring lighter boxes. What number is in the middle box?
  • Add symbols
    plusminus_2 Add marks (+, -, *, /, brackets) to fullfill equations 1 3 6 5 = 10 This is for the 4th grade of the primary school - with no negative numbers yet
  • Two friends
    beers Two friends met as a good man perish together for a beer. After recovery the most important topics (politics, women, football ...), one asks: - And how many do you have children? - I have 3 children. - And how many years have? Friend already not want to a
  • Foot in bus
    havo It was 102 people on the bus. 28 girls had two dogs. A 11 girls had one dog. At the next stop seceded 5 dogs (even with their owners). They got two boys together with three dogs. The bus drove one driver. How many foot were in bus?
  • Math logic
    children_7 There are 20 children in the group, each two children have a different name. Alena and John are among them. How many ways can we choose 8 children to be among the selected A) was John B) was John and Alena C) at least one was Alena, John D) maximum one wa

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