Question

A row of tiny red beads is placed at the beginning and at the end of a 20‐centimeter bookmark.

Answer 1

Answer:

51 rows

Step-by-step explanation:

Given

Length of bookmark = 20cm

Distance between beads = 4mm

Required

Number of rows of beads

First, the distance between the rows of beads must be converted to cm

if 1mm = 0.1cm

then

4mm = 4*0.1cm

4mm = 0.4 cm

This means that each row of beads is placed at 0.4 cm mark.

The distance between each row follows an arithmetic progression and it can be solved as follows;

$T_n = a + (n-1)d$

Where $Tn = 20cm$ (The last term)

$a = 0 cm$ (The first term)

$d = 0.4cm$ (The distance between each row of beads)

n = ?? (number of rows)

Solving for n; we have the following;

$T_n = a + (n-1)d$ becomes

$20 = 0 + (n-1)0.4$

$20 = (n-1)0.4$

DIvide both sides by 0.4

$\frac{20}{0.4} = \frac{(n-1)0.4}{0.4}$

$50 = (n-1)$

$50 = n-1$

Add 1 to both sides

$50 + 1= n-1 + 1$

$n = 51$

Hence, the number of rows of beads is 51