A woman went into a bank to cash an insurance refund check. By mistake the teller gave her dollars for cents and cents for dollars. She put the money in her purse but accidentally dropped a nickel on the floor. When she got home, she found that she had exactly twice the amount of the check she had cashed. She didn't have any money in her wallet before going to the bank. What was the exact amount of that check?
The amount must have been $31.63. She received $63.31. After she dropped a nickel there would remain the sum of $63.26, which is twice the amount of the check.
Con cua cà mau đỏ chạy đua với con cua cà mau xanh. Con cua đỏ có chiều dài càng là 3cm, chân dài 5cm. Con cua xanh có chiều dài càng là 2cm, chân dài 4cm. Tuy nhiên con cua đỏ bị mất 2 cái chân. Hỏi con cua nào chạy nhanh hơn?