地球的近似质量为 $5.97 \times 10^{24}$ kg。地球的重量是一个体重为 125 kg 的相扑选手的多少倍？用科学记数法表示你的答案，并保留 3 位有效数字。 一部手机在线购买的价格为 350 美元。同款手机在新加坡的售价为 600 新元。一家本地商店的老板决定对同款手机进行折扣促销，使其价格等同于买家在线支付的金额。已知 1 美元 = 1.36 新元，计算他必须提供的折扣百分比。 一列火车以 51 km/h 的平均速度行驶了 68 km。然后它又以 40 km/h 的平均速度行驶了 20 km，到达目的地。计算整个行程的平均速度。 在 2020 年，某办公室有 250 名男员工和 300 名女员工。 In the year 2019, the number of male employees was 130% of the current male employees. In the year 2019, the number of female employees was 65% of the current female employees. 求 2019 年男员工与女员工人数的差值占当年女员工人数的百分比。

1. Form and calculate the ratio of the earth's mass to the sumo wrestler's mass.

$\frac{5.97 \times 10^{24}}{125}=4.776\times 10^{22}$

2. Round the answer to 3 significant figures and keep it in standard form.

$4.776\times 10^{22} \approx 4.78\times 10^{22} \quad \text{(3 s.f.)}$

1. Convert the online price to Singapore dollars.

Online price in Singapore dollars:
$350 \times 1.36 = 476$
So the equivalent online price is S$476.

2. Find the discount amount needed from the Singapore price.

Discount needed:
$600 - 476 = 124$
So the shop owner must reduce the price by S$124.

3. Express the discount as a percentage of the original Singapore price.

Percentage discount:
$\frac{124}{600} \times 100\% = 20.666\ldots\%$
$\approx 20.7\%$

1. Find the total distance travelled.

Total distance
$=68+20=88\text{ km}$

2. Find the total time taken for the two parts of the journey.

Using $\text{time}=\dfrac{\text{distance}}{\text{speed}}$,
$\text{Total time}=\frac{68}{51}+\frac{20}{40}$
$=\frac{4}{3}+\frac{1}{2}=\frac{11}{6}\text{ h}$

3. Calculate the average speed for the whole journey.

Average speed
$=\frac{\text{total distance}}{\text{total time}}$
$=\frac{88}{\frac{11}{6}}=88\times\frac{6}{11}=48\text{ km/h}$

1. Find the number of male employees in 2019.

Number of male employees in 2019
$=130\%\times 250=\frac{130}{100}\times 250=325$

2. Find the number of female employees in 2019.

Number of female employees in 2019
$=65\%\times 300=\frac{65}{100}\times 300=195$

3. Express the difference as a percentage of the number of female employees in 2019.

Difference
$=325-195=130$
Required percentage
$=\frac{130}{195}\times 100\%=66.666\ldots\%$
$\approx 66.7\%$