A battery in any household will fit inside a battery-operated toy if, and and only if, that battery is flat.
The duration of a tantrum is equal to or greater than the duration of any telephone call made or received by a parent.
The volume of sandwiches in a lunchbox at 4pm is equal to or greater than the volume of sandwiches in the same lunchbox at 9am.
The time required for a child to recover from illness is equal to the length of time between making and keeping a doctor's appointment.
The combined surface area of items in a toybox is equal to twice the average area of any living room floor.
The depth of any small body of water is always greater than the height of any gumboot.
The volume of items required for an outing equals the capacity of any family car, multiplied by twice the number of children included in the outing.
The number of times a child wakes in any night is equal to the number of alcoholic drinks consumed by the parent during the preceding six hours.
The intensity of a tantrum in a supermarket is proportional to the number of acquaintances of a parent in the same checkout queue, multiplied by the number of items in the parent's shopping trolley.
The number of tantrums produced by the guest of honour at a birthday party is equal to the number of hours spent by a parent in decorating a birthday cake, multiplied by the number of prizes won by other birthday guests.