Depth · one concept from first principles · step 2 of 4
Hazel's 5 large cartons equal 2500 mL, so one large carton is 2500 ÷ 5 = 500 mL.
Finding what one symbol stands for from a known row total is the heart of reading a scaled pictograph.
3.MD.B.3Work BackwardsOne large carton stands for 500 mL.
Hazel's 2500 mL is exactly her five large cartons put together, and every large carton holds the same amount.
Her five cartons cover her whole total with no gaps and no overlaps, so the five carton amounts add back to 2500.
Because the five cartons are equal, adding five of the same amount is the same as five times one carton, so 2500 is five times one carton's value.
Once five times one carton makes 2500, dividing 2500 by five gives the one carton back, so it is 500 mL.
At 500 mL/large, 100 mL/small: Mia=1400, Owen=1800, Hazel=2500, Caleb=2200 mL.
Multiplying each symbol count by its value and adding is direct scaled-pictograph reading.
3.MD.B.3Identify SubproblemsAdd the four amounts: 1400 + 1800 + 2500 + 2200 = 7900 mL.
Combining the four totals is an addition within the thousands using place value.
3.NBT.A.2Identify SubproblemsUse Hazel's row to learn one big carton is 500 mL, then add everyone up - Grade 3 graph reading!
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The same shape shows up later on the AMC, as Arithmetic Expression Decomposition, Coordinate Plane Figure Computation. Why the shapes repeat →