Choose common personal items as a reference. The face length of the fifth set of RMB 50 yuan banknotes is 15cm.

100 yuan notes have a face length of 155mm. Fold the white part on the back of the 100 yuan note in half, and the remaining face length is 15cm. Since the fifth set of RMB 50 yuan banknotes is not very common, we will use RMB 100 banknotes as an operational reference. Unfolding the back of the paper money, we find that the dividing line between white and red is on the left side of the face.

The length of the ruler is 15cm, which can be directly compared.

10, 7 and 5cm size reference:

10 cm: the length of four one-dollar coins arranged side by side, and the diagonal length of the bank card is also 10cm.

7 cm: The fifth set of RMB 10 banknotes is 7 cm long.

5cm: The width of ordinary playing cards is 5cm, and the length of matchbox is 5cm.

Other dimensional references:

2 cm: A 50-cent RMB coin has a diameter of 2 cm.

20cm: The short side length of A4 paper is 20cm.

18 cm: A can of Wangzai milk is exactly 9 cm high, and when two cans of Wangzai milk overlap, it is 18 cm.

1m: The short side of the window is usually 1m long.