A pieces of ribbon is 5m 20cm long. 60cm of the ribbon is cut off to tie a parcel. After that, the remaining ribbon is cut into 4 equal pieces. What is the length of each piece of ribbon?

The average mass of a group of 6 adults is 65 kg and the average mass of another group of 4 adults of 80kg. What is the average mass of all the adults in the 2 groups?

Mrs Conchie bought 6m 20cm of ribbon and used up $\frac{3}{4}$ of it. She cut the remaining ribbon into 5 equal strips. How long is each strip of ribbon?

Benjamin has a square piece of paper. He cuts along the dotted lines shown in Figure 1 to get the shaded part and 8 identical isosceles triangles. Triangle PQR in figure 2 is one such triangle with a perimeter of 16cm. The ratio of the perimeter of the square paper to the perimeter of the shaded part is 1:2. Find the length of PQ.

The volume of a cuboid with a height of 7m is 252m$^3$. All the sides of the cuboid are whole numbers. Which one the following in not a possible length of the cuboid?