Let workdone 1 boy in 1 day be b

and that of 1 girl be g

From the given data,

4(5b + 3g) = 23

20b + 12g = 23 .......(a)

2(3b + 2g) = 7

6b + 4g = 7 ........(b)

Solving (a) & (b), we get

b = 1, g = 1/4

Let number og girls required be 'p'

6(7 x 1 + p x 1/4) = 45

=> p = 2.

Hence, number of girls required = 2

The major greenhouse gases (GHG’s) solely responsible for greenhouse effect are Carbon dioxide, Ozone, Methane and Water vapor. Although these gases comprise 1% of our atmosphere, they act like a thick warm blanket outside that surrounds this planet and regulate climate control. Greenhouse effect is not bad. In fact, it is needed for all of us to survive on planet Earth. In short, the greenhouse effect is nothing but a naturally occurring process designed by nature that aids in heating earth’s surface and helps to maintain ecological balance.

Now, while some of that heat dissipates into space, some of it burns along the atmosphere, and some of it penetrates the atmosphere and finds its way into the lower atmosphere and the planet’s surface. This in turn raises the average temperature of the Earth. Therefore, the increase in the Earth’s surface temperature due to increase in the number of greenhouse gases leads to global warming.

Causes of Green House Effects ::

* Burning of Fossil Fuels

* Deforestation 

* Increase in Population

* Farming

* Industrial Waste and Landfills.

Romans (753 BC - AD 410) began public health and sanitation systems.

Romans established the first public health and sanitation systems by building sewers and aqueducts.

They also treated diseases with diet, exercise and meditation.

Jeff Bezos is the richest person in modern history. The Amazon.com Inc. founder’s net worth broke $150 billion in New York on 16th July 2018 morning, according to the Bloomberg Billionaires Index.

That’s about $55 billion more than Microsoft Corp. co-founder Bill Gates, the world’s second-richest person.

Drinking alcohol can cause many damages to your body. Your vision can be affected as you will face blurred and double vision and even you can't identify colors.

There are many differences between cancer cells and normal cells. Some of the differences are well known, whereas others have only been recently discovered and are less well understood.

Cancer Cells vs. Normal Cells ::

Below are some of the major differences between normal cells and cancer cells, which in turn account for how malignant tumors grow and respond differently to their surroundings than benign tumors.

Growth :—

Normal cells stop growing (reproducing) when enough cells are present. For example, if cells are being produced to repair a cut in the skin, new cells are no longer produced when there are enough cells present to fill the hole; when the repair work is done. In contrast, cancer cells don’t stop growing when there are enough cells present. This continued growth often results in a tumor (a cluster of cancer cells) being formed. 

Communication :—

Cancer cells don’t interact with other cells as normal cells do. Normal cells respond to signals sent from other nearby cells that say, essentially, “you’ve reached your boundary.” When normal cells “hear” these signals they stop growing. Cancer cells do not respond to these signals.

Stickiness :—

Normal cells secrete substances that make them stick together in a group. Cancer cells fail to make these substances, and can “float away” to locations nearby, or through the bloodstream or system of lymph channels to distant regions in the body.

Ability to Metastasize (Spread) :—

Normal cells stay in the area of the body where they belong. For example, lung cells remain in the lungs. Cancer cells, because they lack the adhesion molecules that cause stickiness, are able to travel via the bloodstream and lymphatic system to other regions of the body—they have the ability to metastasize. 

Appearance :—

Under a microscope, normal cells and cancer cells may look quite different. In contrast to normal cells, cancer cells often exhibit much more variability in cell size—some are larger than normal and some are smaller than normal. In addition, cancer cells often have an abnormal shape, both of the cell, and of the nucleus (the “brain” of the cell.) 

The rate of growth :—

Normal cells reproduce themselves and then stop when enough cells are present. Cancer cells reproduce rapidly before the cells have had a chance to mature.

Maturation :—

Normal cells mature. Cancer cells, because they grow rapidly and divide before cells are fully mature, remain immature. Doctors use the term undifferentiated to describe immature cells (in contrast to differentiated to describe more mature cells.) 

Evading the immune system  :—

When normal cells become damaged, the immune system (via cells called lymphocytes) identifies and removes them. Cancer cells are able to evade (trick) the immune system long enough to grow into a tumor by either by escaping detection or by secreting chemicals that inactivate immune cells that come to the scene.

Functioning :—

Normal cells perform the function they are meant to perform, whereas cancer cells may not be functional. For example, normal white blood cells help fight off infections. In leukemia, the number of white blood cells may be very high, but since the cancerous white blood cells are not functioning as they should, people can be more at risk for infection even with an elevated white blood cell count.

Add the letter 'G' to the word 'ONE' and it become's 'Gone' which means disappear.

A glove. It has 5 fingers as we have but not alive.