赵和梅正在规划他们的运动计划。 他们记录了自己的体重以及步行和慢跑的速度。

1. Find the time for one walk

The 4 brisk walks together meet the minimum target of $150$ minutes.

Time for one walk:
$150 \div 4 = 37.5\text{ minutes}$
$37.5\text{ minutes} = \frac{37.5}{60}\text{ h} = 0.625\text{ h}$

2. Use speed and time to find the distance of one walk

Brisk walking speed $=5\text{ km/h}$.

$\text{Distance}=\text{speed}\times\text{time}$
$=5\times 0.625=3.125\text{ km}$

1. Find the difference in calories used per 30 minutes and scale it to 150 minutes

From the table, for walking at $5\text{ km/h}$ for $30$ minutes:

Zhao uses $135$ calories and Mei uses $120$ calories.

Difference per $30$ minutes:
$135-120=15$

The total walking time is $150$ minutes, so
$150\div 30=5$

Difference for all $4$ walks:
$15\times 5=75$

1. Find Zhao's weekly aerobic exercise time in moderate-equivalent minutes

Zhao walks $4\text{ km}$ at $5\text{ km/h}$, so time for one walk
$=\frac{4}{5}\text{ h}=0.8\text{ h}=48\text{ min}.$
For $3$ walks, walking time
$=3\times48=144\text{ min}.$
Zhao jogs $6\text{ km}$ at $8\text{ km/h}$, so time for one jog
$=\frac{6}{8}\text{ h}=0.75\text{ h}=45\text{ min}.$
For $2$ jogs, jogging time
$=2\times45=90\text{ min}.$
Since $1$ min vigorous $=2$ min moderate, Zhao's moderate-equivalent time
$=144+2(90)=324\text{ min}.$

2. Check whether Zhao meets his target for additional health benefits

For additional health benefits, Zhao needs $300$ min moderate activity or an equivalent combination.

Since
$324\text{ min}>300\text{ min},$
Zhao meets his target for exercise.

3. Find Mei's weekly aerobic exercise time and check her target

Mei jogs $8\text{ km}$ at $9.5\text{ km/h}$, so time for one jog
$=\frac{8}{9.5}\text{ h}=\frac{16}{19}\text{ h}.$
For $2$ jogs, jogging time
$=2\times\frac{16}{19}\text{ h}=\frac{32}{19}\text{ h}=101.05\ldots\text{ min}.$
Mei needs at least $75$ min of vigorous activity for recommended health benefits.

Since
$101.05\ldots\text{ min}>75\text{ min},$
Mei meets her target for exercise.

4. Calculate Zhao's total weekly calories used

From the table, Zhao uses $135$ calories per $30$ min walking at $5\text{ km/h}$.

Zhao walks for $144$ min, so walking calories
$=135\times\frac{144}{30}=648.$

From the table, Zhao uses $315$ calories per $30$ min jogging at $8\text{ km/h}$.

Zhao jogs for $90$ min, so jogging calories
$=315\times\frac{90}{30}=945.$

Yoga uses $3$ calories per kg per hour. Zhao's body weight is $80\text{ kg}$, and he does two $45$-minute classes:
$2\times45\text{ min}=90\text{ min}=1.5\text{ h}.$
Yoga calories
$=3\times80\times1.5=360.$

Total calories for Zhao
$=648+945+360=1953.$

5. Calculate Mei's total weekly calories used

From the table, Mei uses $345$ calories per $30$ min jogging at $9.5\text{ km/h}$.

Mei jogs for $101.05\ldots$ min, so jogging calories
$=345\times\frac{101.05\ldots}{30}=1162.105\ldots.$

Weight training uses $4$ calories per kg per hour. Mei's body weight is $70\text{ kg}$, and she does two $30$-minute sessions:
$2\times30\text{ min}=60\text{ min}=1\text{ h}.$
Weight training calories
$=4\times70\times1=280.$

Total calories for Mei
$=1162.105\ldots+280=1442.105\ldots.$

6. Compare Zhao's calories with Mei's and decide whether Zhao's statement is correct

Percentage more calories Zhao uses than Mei
$=\frac{1953-1442.105\ldots}{1442.105\ldots}\times100\%$
$=35.4\%\text{ approximately}.$

This is not about $50\%$ more.

Therefore, Zhao is only partly correct: both meet their exercise targets, but he does not use about $50\%$ more calories than Mei.