Problems of the Week

Dec 16, 2019 | High Park

Mathletes! Have a go at solving these brain teasers!

Lower Elementary:

Question: Allison brings a box of 24 gumdrops to school one morning. She ate half of the gumdrops at lunch. At afternoon recess, she ate half of the gumdrops she had left. How many gumdrops does Allison have left after recess?

 

Upper Elementary:

Question: There are 10 knitters in a knitting club. Each knitter makes 18 hats per month. The knitting club takes all the hats and packs them in boxes of 12. How many boxes of hats can the knitting club fill in a month?

 

Middle School:

Question: Mason uses a promo code to get 20% off a video game console, plus free shipping! If the cost of the video game console is $450 and sales tax is 10% where Mason lives, then what is the final cost of the video game console?

 

Algebra and Up:

Question: What is the sum of all whole numbers from 1 to 100?

 

 

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Answers:

 

Lower Elementary:

Answer:  6 gumdrops

Solution:  Allison ate half of her gumdrops for lunch. Half of 24 is 12. She then ate half of those 12 gumdrops during recess. Half of 12 is 6. So, Allison has 6 gumdrops left after recess is over.

 

Upper Elementary:

Answer:  15 boxes

Solution:  To find the total number of hats, we multiply the number of knitters by the number of hats they each make: 10 × 18 = 180 hats. Each box holds 12 hats, so we divide 180 hats into groups of 12: 180 ÷ 12 = 15 groups of 12 hats. So, the knitting club can fill 15 boxes.

 

Middle School:

Answer:  $396

Solution:  The video game console costs $450 before the discount, $450 × 0.8 = $360 after the 20% discount, and $360 × 1.1 = $396 after the 10% sales tax.

 

Algebra and Up:

Answer:  5,050

Solution:  Instead of adding up all the numbers individually, we can match pairs of numbers that make 100. If you write the first few and the last few numbers of the series, it will read 1 + 2 + 3 + … + 97 + 98 + 99 + 100. Notice that 99 + 1 = 100, 2 + 98 = 100, 3 + 97 = 100, etc. After all the pairs are matched up, we will have 49 pairs of numbers that will equal 100, the 100 at the end, and the 50 in the middle. 100 × 50 + 50 = 5,050.