Can you solve these 10 Singapore primary maths questions?

Maths and logical thinking have proven to be extremely beneficial to a child’s development. Kids learn how to recognise patterns, sequences, seriation, spatial relationships, object permanence, etc. These skills can be cultivated early by letting children play with educational toys and cubes and by helping them learn with maths workbooks, which can be found on sites like Hope Education.

Maths seems to be one of those subjects at school that you either love or hate. But many think that primary school maths questions should be solvable by everybody. We’ve put together a list of 10 maths problems that primary school pupils from Singapore are faced with on a daily basis. See if you’ve got what it takes to crack these logic puzzles.

Ella enters the forest of forgetfulness and meets a lion and a unicorn. The lion lies on Mondays, Tuesdays, and Wednesdays, the other days he speaks the truth. The unicorn lies on Thursdays, Fridays, and Saturdays and speaks the truth on all other days. The lion says: “Yesterday I was lying.” to which the unicorns responds: “So was I.” On what day did they say that?

The king sentenced you to death, but he gives you a chance to be set free. He hands you 50 white marbles, 50 black marbles, and two empty bowls. He asks you to divide the 100 marbles in any way you like among the two bowls. You’ll then be blindfolded while the king will mix the bowls around. Then you’ll have to choose one bowl and pick one marble. If the marble is white, you’re free, if it’s black, you die. How would you divide the marbles to have the best chance of being set free?

A little girl is 2 years old, but her sister is only half as old as her. When the first girl is 100, how old will her sister be?

A woman has to get a fox, a goose, and a sack of corn across a river. Since she only has a small rowing boat, she can only take herself and one other thing with her. If she leaves the goose and the fox alone together, the fox will eat the goose. If she leaves the goose and the corn alone together, the goose will eat the corn. How can she transport everything and make sure that all of them arrive safely on the other side?

You and a friend have the same amount of apples. How many apples does your friend need to give you for you to have 10 more than him?

You need to measure exactly 6 gallons of water, but you only have a 4-gallon and a 7-gallon jug to work with. How do you do it?

Sally and Dave both have some pears. If Sally gives Dave a pear, they’ll both have the same amount. However, is Dave gives Sally a pear, then Sally will have twice as many as Dave. How many pears do they each have?

Your sock drawer is full of unpaired black and white socks. If you close your eyes, how many times will you have to reach in to guarantee having a matching pair?

A girl and her big brother are sitting at the table. The girl says: "If I take two years away from my age and gave them to you, you'd be twice my age." The brother replies: "Why don't you just give me one more and then I'll be three times your age." How old are the siblings?

Six-year-olds can crack this puzzle in about 20 seconds while most adults are stumped. Do you know the answer?

Answers:

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1. There’s no day when both would be lying, so at least one of them is telling the truth. Both speak the truth on Sunday; however, the lion would then be lying in his statement so it couldn’t be Sunday. One of them is lying. If the unicorn was honest, it’d be Sunday, but we’ve proven this to be wrong. Hence the lion and unicorn said their statements on Thursday talking about Wednesday.

2. Place one white marble in a bowl and all the others marbles in the other bowl (49 whites and 50 blacks). That way you begin with a 50/50 chance of choosing the bowl with only one white marble in. Even if you choose the other bowl, you still have an almost 50/50 chance of picking a white marble.

3. 99

4. First she and the goose cross the river. She leaves the goose on the other side and goes back to take the fox. Since she can’t leave the fox and the goose together, she takes the goose back. Then she takes the corn and leaves it with the fox. Finally, she goes back one more time to pick up the goose.

5. He needs to give you 5 apples. Both of you will need at least 5 apples to begin with, but after that it doesn’t matter how many apples you both have. When he gives you 5, he’ll lose 5 and you will gain 5 resulting in a net difference of 10.

6. Completely fill up the 7-gallon jug. Now pour as much of the 7 gallons as you can into the 4-gallon jug. This should leave you with 3 gallons in the 7-gallon jug. Pour out the 4-gallon jug, and transfer the 3 gallons from the 7-gallon jug into the 4-gallon container. Finally, fill up the 7 gallon jug completely again and pour what you can (1 gallon) into the 4-gallon jug. This should leave you with 6 gallons in the 7-gallon jug.

7. Sally has 7 pears and Dave has 5 pears.

8. 3 times

9. They’re both 6 years old and would have to have been born within one year of each other.

10. 87. The numbers are upside down.

Sources:

http://resources.woodlands-junior.kent.sch.uk/fun.html

http://www.fitbrains.com/blog/friday-fun-brain-teasers/

http://www.dailymail.co.uk/news/article-3127520/Are-smarter-Hong-Kong-grader-Logic-puzzle-Chinese-primary-school-exam-stumps-adults-6-year-olds-crack-just-20-seconds.html

http://www.education.com/reference/article/mathematics-development/

http://www.squiglysplayhouse.com/BrainTeasers/MathGames.php