A cube has six differently coloured faces. Paul sees blue, white, yellow; Sally sees black, blue, red; Betty sees green, black, white. What colour is opposite white?
Tùng rides from home to work at 30 km/h. Returning, he travels half the distance at the same speed, then spends 10 minutes repairing his motorbike. To make the total return time equal to his morning journey time, he travels the remaining half at 50 km/h. How far is work from home?
Tom may place a counter in any cell of a 3 × 3 grid, then move horizontally or vertically, never diagonally. From how many starting cells can he visit every cell exactly once?
Jenny places six dice in a straight row. Opposite faces of each die have a total of 7 dots. What is the greatest possible sum of dots over all exterior faces of the resulting block?
As in the source, count every exterior face, including the underside and the two ends.
Three cars enter a roundabout from different roads simultaneously, as shown. None completes a full circuit, and no two leave by the same road. How many different assignments of exit roads are possible?
Kelly cuts a 27 cm ribbon into four rectangles of arbitrary lengths. She joins the centres of the first pair and of the last pair of adjacent rectangles as shown. What is the sum of the two segment lengths?
A three-digit number is called “certain” if its hundreds digit equals the sum of its other two digits. For example, 431 is certain because 4=3+1. How many three-digit certain numbers exist?
Seven equal-length rulers are arranged in two staggered rows as shown. Each ruler is 14 cm long and the whole span is 80 cm. What is the marked overlap length?
Snow White gives whole candies to seven dwarfs, at least one each. The youngest gets twice as many as the oldest, and the other five get equal numbers. Which statement about the total is certainly correct?