
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
An isosceles right triangle with legs of length 10 is partitioned into 25 congruent triangles. Calculate the area of the shaded region if 15 of these smaller triangles are shaded.
A) 20
B) 25
C) 30
D) 35
E) 40

Present the answer in LaTex format: \boxed{Your answer}
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