Shapes, units & dates — cards for areas and volumes, unit conversion and days between dates

The three cards on the left are inputs: the tank's depth 30, width 60 and height 36, in cm. The Figure card in the middle is a cuboid, with the three connected in the order depth → width → height. Its volume is 30×60×36 = 64,800, in cm³. The Unit conversion card on the right changes this value from mL to L. One cm³ is one mL, so 64,800 mL is 64.8 L.

With the height set to 30, the volume becomes 54,000, which is 54 L. The Figure card shows no unit, so the unit is read from the inputs.

Figure

Given length cards in order, it draws the shape and works out its area; for a solid, its volume. The menu at the top of the card offers 13 shapes. Under the drawing, the card shows the formula with the connected numbers, and the answer. Connected to another card, it passes this answer (the area or the volume) on.

The order of the connections matters. For each shape it is as follows.

With too few cards connected, the card shows the order to connect them in, such as "Connect base → height". When a length or angle is negative, or a sector's central angle is over 360°, the card says so instead of drawing. The circumference, arc and hypotenuse are only written on the drawing; the value passed on is the area.

For a cuboid, cube, cylinder or cone, pressing "Net" next to the shape menu shows the net and the surface area. For the tank on Board 1 as it opens, the surface area is (30×60 + 60×36 + 30×36) × 2 = 10,080. The value passed on stays the volume while the net is shown. For a prism, pyramid or sphere, pressing "Net" shows why it cannot be unfolded: the shape of a prism's or pyramid's base is not known, and a sphere's curved surface cannot be laid flat.

On Board 2, the same two cards, a and b, are connected to a triangle and a parallelogram. a and b are input cards shown as sliders, moving from 1 to 10 in steps of 1. At the starting values a = 6 and b = 4, the triangle is 6×4÷2 = 12 and the parallelogram 6×4 = 24. With a set to 9, the triangle becomes 18 and the parallelogram 36. However a and b move, the triangle is exactly half the parallelogram.

Unit conversion

Given one value card, it changes the value into another unit. The menu at the top of the card picks the quantity, and the two menus below pick the unit to convert from and the unit to convert to. "⇄" swaps the two units. Connected to another card, it passes the converted value on.

The card shows the original value, how it is converted (such as "↓ ÷1,000"), and the converted value, one under the other. On Board 1 as it opens, these are "64,800 mL", "↓ ÷1,000" and "64.8 L". A temperature cannot be converted by multiplying alone, so from °C to °F the card shows "×1.8 +32". 25 °C is 77 °F.

The connected value is read as a value in the "from" unit. A unit written on an input card is for display only, so the "from" unit is chosen to match the number supplied. KB, MB, GB and TB go up by 1,000 each, and one gal is 3.785412 L (the US gallon). A temperature below −273.15 °C makes the card say that no such temperature exists.

Open the unit conversion board that turns minutes into hours ↗

Dates & durations

It gives the number of days between two dates, or the date a number of days after a given day. The menu at the top of the card chooses between "Days between two dates", "Date after n days" and "Days from today until". Dates and the number of days are entered in the card's fields; they cannot come from other cards through a connection. A newly placed card shows "Days between two dates" from today to 30 days later.

The top card on Board 3 is "Days between two dates": from 1 January to 31 December 2026 is 364 days. It is a difference, so the first day is not counted. Counting both ends, as the calculation card on the right does by adding 1, gives 365 days. The small text underneath gives the same span in months and days, and in weeks and days: "11 mo 30 d ／ 52 weeks". When the end date is before the start date, the number of days is negative and the text ends in "back".

The bottom card is "Date after n days": 100 days after 1 October 2026 is 2027-01-09. A negative number of days gives a date that many days earlier. The number of days has to be a whole number. "Days from today until" counts from today to the "To" date, so it changes from day to day.

The number of days is passed on to other cards in "Days between two dates" and "Days from today until". "Date after n days" only shows a date; a calculation card that uses it shows that the card it refers to has no value. The card does not show the day of the week.

Articles that use these cards

• Area of a triangle — one base and one height are connected to triangle, parallelogram and right-triangle Figure cards to compare their areas.
• Unit conversion — Unit conversion cards are chained in two steps for lengths, with conversions of areas and times as well.

Read next — Basics Calculation, input, memo, list, simulation and the other cards that most boards are built on.

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