Tough Singapore math questions

I have been reading the testimony of John Hoven On Behalf of The Center for Education Reform on the Draft 2004 Mathematics Framework for the National Assessment of Educational Progress (NAEP).

In his testimony, Mr. Hoven compares the type of questions Singapore students are asked to the toughest NAEP questions which turn out to be fluff in comparison. Not only that, the much tougher Singapore questions are asked in much lower grades.

Mr. Hoven's testimony contains numerous examples from Singapore's tests. It's hard to imagine something like this happening here.

Here are a few examples:

Singapore students learn the concept of percentages in 5th grade, and they work much harder problems without a calculator – like these:

1 3 ) A blouse and a skirt were sold at a discount of 25% if they were bought together. If bought separately, the blouse would cost $25 and the skirt would cost 30% more than the blouse. How much would the blouse and skirt cost after the discount if they were bought together? Give your answer to the nearest cent.

1 4 ) A bank pays interest at a rate of 4% every year. If Christine has $5000 in the bank, how much money will she have altogether after 2 years?

1 5 ) 30% of the marbles in a box were blue. 45% of them were green and the rest orange. If there were 200 more blue marbles than orange ones, how many marbles were in the box?

Here is a 6th grade Singapore problem on proportionality:

1 6 ) A basket of clothes, when half full, weighed 2.4 kg. The basket became 5/8 full when another 0.5 kg of clothes were added in. What was the weight of the empty basket?

This is fifth and sixth grade!