[Pri20151117MSAS] MCQ tactic for the Area of a Hollow Square

Question

Solution 1

     Width of the smaller square  WX = (156 ¸ 4) cm   = 39 cm

     Width of the larger square     AB = (39 + 2´8) cm = 55 cm

     Area = (55² – 39²) cm² = 1504 cm² 

     Ans: (1)

Solution 2

     This is a Multiple Choice Question (MCQ).  Observe that the shaded area is an even number, because it is 8 cm width all around.  Since 1504 is the only even number among the options, (1) is the correct choice.

Remark

     No tedious calculation is needed!

Heuristics Used

H02. Use a diagram / model

H04. Look for pattern(s)

H09. Restate the problem in another way

H10. Simplify the problem

H11. Solve part of the problem

Suitable Levels
* Primary School Mathematics
* other syllabuses that involve areas and perimeters
* anyone who loves his/her brain tickled