P5 Math: Tank A and Tank B

Tank A and Tank B contained 12.5L of water altogether. 3/5 of the water from tank B was transferred into tank A. 4/9 of the water from Tank A was then transferred into tank B. Both tanks contained an equal volume of water in the end. How many litres of water did each tank contain at first? Give answer in mixed number.

Solution:

At the end there will be five boxes on TA and TB on Step (1). Where is it coming from ?

• See final figure on Step (1). when four boxes transferred from TA to TB. In order to have five boxes on TB, there should be one original box there.
• Now, return the four boxes back to TA. The situation before transfer is described in Step (2) figure
• Check Step (3), to see how 2 units of TB left on TB while 3 of its units transferred to TA.
• 2 units on TB need to duplicate to TA too since the box is in the similar size
• Each unit is named u.
• Return the 3 brown units on Step 3 from TA to TB. Now we can see the original (at first) condition.

So, total 15u + 5u = 20u = 12 1/2, or u = 5/8

At first, 

• Tank A had 15u = 75/8 = 9 3/8 L
• Tank B had  5u  = 25/8 = 3 1/8 L

Method 2

Use similar method as explained in p5-math-calvin-and-susie page.