Category: Teaching Ratios

Measuring Noah’s Rainbow Arc

Have your class make a homemade Noah’s arc.  You will need creative materials:

a ruler

a tetra pack or other recycled container that floats

sticky pine pitch or an eco-friendly sealant

other thoughtful decorative creative materials

In the bible, Noah is instructed to make an arc large enough and strong enough to fit a lot of animals and to last in the flood that is to come.  The name Noah is noted as “comforter”:  Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch.  (Blue Letter Bible; Genesis 6:14)…And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits.  (Blue Letter Bible Genesis 6:15.  A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it.  (Genesis 6:16) (This passage could either be 4 stories in Height in its description, or 3, depending how it is interpreted – is the lower basement floor considered to be counted as a floor.  The passage in Genesis (Genesis 6:15) says that God instructed Noah to build the Arc in these dimensions using Cubits.  The cubit is an ancient unit based on the forearm length from the tip of the middle finger to the bottom of the elbow.  The estimate varies depending on which version of a biblical text one reads.  Approximately 17.5-20.6 inches (  What in Today’s world can be compared with The Length of Noah’s Arc about 450 Feet Long?  a Baseball Field; a 7 story Building.  There would be 3-4 stories of height (including the lower) and a giraffe would have to fit (approximately and up to 15-18 feet)!  How tall is a giraffe?

Cubits Answer:

300 Cubits = 450’ L

50 Cubits = 75 ‘ W

30 Cubits = 45 ‘ H

where L = Length

           W = Width

           H = Height

Metric Conversion (where 1 inch – 2.5 cm):

L   300mm = 30cm

W 50 mm = 5cm

H 30 mm = 3 cm

Have your class find homemade materials from the recycle bucket or pieces of materials that your folks have no need for, and make a miniature version of the arc as it is described.  Fashion a window 18 inches from the roof, and make a door.

Rainbow Covenant (Genesis 9:11-16… And I will establish my covenant with you; neither shall all flesh be cut off any more by the waters of a flood; neither shall there any more be a flood to destroy the earth….And God said, This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations:…And I shall set my bow in the cloud, and it shall be for a token of a covenant between me and the earth….


(Photo Here)

Our homemade prototype turned out to be 12 inches x 1 inch x 1.5inches, with a window just under the top, and it floats!  Have fun decorating your Arc as you would be living it for 150 days before the waters receded.  Pine Tar is a term for what is called “Pitch”.   It can act as a sealer for the bottom of your arc, but be careful as it is sticky stuff!  Have fun!

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Writing Mathematical Ratios

Comparing numbers and quantities can be an advanced component of teaching Math, but can also be easily introduced to younger students in first or second grade. In Math, it is important to provide all students with mathematical vocabulary, like ratio or proportion. (Dice; downloaded Feb. 7, 2014;  A ratio is nothing more than a comparison of two quantities and we use ratios even outside of the classroom. For example, when cooking, we may use 2 parts flour to 1 part sugar, that would be the ratio 2 : 1 or when mixing cleaning products, like 1/3 cup of bleach to 1 gallon of water. It is essential to explain complex terms like ratio or proportion in easy to understand language, and when possible using hands-on everyday items.

In this activity students will learn how to calculate and write a ratio.


5 sealable bags, red/blue/green marbles or unit blocks (20 of each color), white board, dry erase markers *This is best done as a group activity with no more than 4 students per group. Prior to the activity, place a different amount of each marble color in each sealable bag. For example, Bag 1 may have 3 green, 4 blue, and 5 red. Label each bag with a number to better keep track of the bags and marbles used.


  1. Assemble the class into small groups.
  2. Give each group a labeled bag of marbles.
  3. Have the students count the total number of marbles in the bag and the number of marbles of each color and record the data on a piece of paper.
  4. Have the groups rotate bags so that each group gets a new sealable bag and repeat steps 2 and 3.
  5. Ask the students: “What did you notice about the number of marbles in each bag? What about the number of each color?”
  6. Explain to the students that the number of each color marble can be written as a ratio or a comparison. You may consider saying, “A ratio is a number that compares to items together. For example, in Bag 1, there were 3 blue marbles and 5 red marbles, so we could compare or write a ratio of blue marbles to red marbles by writing 3 : 5.”

For older students, consider extending the activity by providing them with word problems involving ratios. Have them explore how ratios can be maintained by doubling or halving quantities. For example, you might ask, “if the marbles are to stay in a 3 : 1 ratio, how many marbles of each color would you need if you wanted to double the total number of marbles in Bag 3?”

Ratio activities can be a great tool to teach fractions in the classroom. For more creative math teaching tips, visit: and .

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