It is known that in January there are four Fridays and four Mondays. What day of the week is January 1st?
How, without any means of measurement, can you measure a length of 50 cm from a shoelace, whose length is \(2/3\) meters?
Find out the principles by which the numbers are depicted in the tables (shown in the figures below) and insert the missing number into the first table, and remove the extra number from the second table.
Find a two-digit number that is 5 times the sum of its digits.
Will the quotient or the remainder change if a divided number and the divisor are increased by 3 times?
Try to get one billion \(1000000000\) by multiplying two whole numbers, in each of which there cannot be a single zero.
Ten people wanted to found a club. To do this, they need to collect a certain amount of entrance fees. If the organizers were five people more, then each of them would have to pay £100 less. How much money did each one pay?
A cube with a side of 1 m was sawn into cubes with a side of 1 cm and they were in a row (along a straight line). How long was the line?
Seven nines written out in a series: 9 9 9 9 9 9 9. Put some “\(+\)” or “\(-\)” between some of them, so that the resultant expression equals 1989.
The tower clock chimes three times in 12 seconds. How long will six chimes last?