Uncle Zak runs out of battery power whilst searching in his dustcart. Amber and Sam are enlisted to bring spare batteries. When they arrive they find that Uncle Zak is not there, and the batteries are not the same size as his. They think they could use them anyway and ask Numberella for help. She confirms their suspicion that one half is the same as two quarters or even five tenths. With this advice the children are able to replace the batteries with their equivalents, and Uncle Zak is very impressed.