Читать книгу The Ultimate Mathematical Challenge: Over 365 puzzles to test your wits and excite your mind - Литагент HarperCollins USD, F. M. L. Thompson - Страница 23
Оглавление71. A magic square
In a magic square, each row, each column and both main diagonals have the same total.
In the partially completed magic square shown, what number should replace N?
72. Fly, fly, fly away
In this addition sum, each letter represents a different non-zero digit.
What are the numbers in this sum?
73. What is the units digit?
Catherine’s computer correctly calculates
What is the units digit of its answer?
74. Minnie’s training
After a year’s training, Minnie Midriffe increases her average speed in the London Marathon by 25%.
By what percentage did her time decrease?
75. Telling the truth
The Queen of Hearts always lies for the whole day or always tells the truth for the whole day.
Which of these statements can she never say?
A. ‘Yesterday, I told the truth.’
B. ‘Yesterday, I lied.’
C. ‘Today, I tell the truth.’
D. ‘Today, I lie.’
E. ‘Tomorrow, I shall tell the truth.’
76. What is the unshaded area?
Eight congruent semicircles are drawn inside a square of side length 4.
Each semicircle begins at a vertex of the square and ends at a midpoint of an edge of the square.
What is the area of the unshaded part of the square?
77. Aimee goes to work
Every day, Aimee goes up an escalator on her journey to work. If she stands still, it takes her 60 seconds to travel from the bottom to the top. One day the escalator was broken so she had to walk up it. This took her 90 seconds.
How many seconds would it take her to travel up the escalator if she walked up at the same speed as before while it was working?
