An L-shaped tile is made of four unit squares, as shown. How many of the five shapes below can be made by joining two such tiles? Practice clarification: the tiles may be rotated and turned over.
We have three identical water pipes. The figure shows a total length of 355 cm when two are joined and 530 cm when three are joined. What is the length of one pipe?
Numbers are arranged in a triangle as shown. There are 3 numbers in row 2 and 5 numbers in row 3. Following the same pattern, what is the first (leftmost) number in row 20?
A team of 14 workers repairs a road in 15 days. If 16 more workers join the team, how many days will the same repair take? Editorial clarification: every worker works at the same constant daily rate.
Thanh selects three numbers from the $3\times3$ table below, choosing exactly one number from each row and each column. What is the greatest possible product of the three selected numbers?
A rectangular wall pattern uses two types of tiles: grey tiles and striped tiles. Some tiles have fallen off, as shown. How many grey tiles have fallen off?
Class 5A is divided into 8 groups with equal numbers of pupils to plant trees. The class plants 215 trees in total. Each girl plants 5 trees and each boy plants 6 trees. How many girls are in the class?
A digital clock displays every minute of the day from 00:00 to 23:59. How many displayed times contain exactly two digits 0? For example, 05:10 and 10:10 both satisfy the condition.
Fill a $3\times3$ grid with the numbers 1 to 9, using each exactly once. The product of the middle row is 45 and that of the middle column is 162, as shown. Find $A+B+C+D$.
Nhi and five friends each roll a six-sided die numbered 1 to 6. All six results are different. The product of her five friends’ results leaves remainder 4 when divided by 7. What number did Nhi roll?
The sum of the areas of the two triangles below is $120\text{ cm}^2$ (the diagram is not to scale). The shaded overlap is $\frac13$ of the smaller triangle and $\frac19$ of the larger triangle. Find the shaded area in square centimetres.