MYTS 2019 - Grade 3 - Round 2

A rectangular field has perimeter 42 metres. If its length is reduced by 5 metres, its area decreases by 30 square metres. Find the area of the original field. (Enter the number of square metres.)

A box contains blue, red and yellow marbles. The number of red marbles is half the number of blue marbles and twice the number of yellow marbles. There are 48 more blue marbles than red marbles. How many marbles are there altogether?

From Châu’s birthday last year through the last day of that year, her mother gave her one blue paper crane every morning. This year, her mother has given her one red paper crane every morning. On the evening of February 27, Châu finds that she has equal numbers of red and blue cranes. On what date is her birthday?

Show how to pack 10 bags of rice and 10 bags of corn into four empty containers so that no container holds more than 20 kg. Each bag of rice weighs 5 kg and each bag of corn weighs 3 kg.

A box contains nine cards bearing the numbers 11, 20, 25, 27, 42, 45, 49, 54, 58. Bắc, Trung and Nam take turns, in some order, removing cards according to these rules:

- Bắc takes every even-numbered card still in the box when it is his turn.
- Trung takes every odd-numbered card still in the box when it is his turn.
- Nam takes every card whose digit sum is even, still in the box when it is his turn.

Afterward each friend has at least one card, and their numbers of cards are all different. Who took cards first? Explain why.